feat(admin): add admin panel for student management

Backend:
- Admin DTOs for student management views
- Admin queries for listing all students with activation status

Frontend:
- AdminDashboard: overview of all students
- StudentManagement: CRUD operations with activation controls
- Manual activation toggle for administrators
- Filter by activation status
- Bulk operations support

This enables administrators to manage student accounts,
manually activate accounts, and monitor registration status.

src/backend/Application/Admin/DTOs/AdminStatsDto.cs

@@ -0,0 +1,14 @@
+namespace Application.Admin.DTOs;
+
+public record AdminStatsDto(
+    int TotalStudents,
+    int TotalEnrollments,
+    double AverageCreditsPerStudent,
+    SubjectStatsDto? MostPopularSubject,
+    IReadOnlyList<SubjectStatsDto> SubjectStats);
+
+public record SubjectStatsDto(
+    int SubjectId,
+    string SubjectName,
+    string ProfessorName,
+    int EnrollmentCount);

src/backend/Application/Admin/Queries/GetAdminStatsQuery.cs

@@ -0,0 +1,50 @@
+namespace Application.Admin.Queries;
+
+using Application.Admin.DTOs;
+using Domain.Ports.Repositories;
+using MediatR;
+
+public record GetAdminStatsQuery : IRequest<AdminStatsDto>;
+
+public class GetAdminStatsHandler(
+    IStudentRepository studentRepository,
+    ISubjectRepository subjectRepository)
+    : IRequestHandler<GetAdminStatsQuery, AdminStatsDto>
+{
+    public async Task<AdminStatsDto> Handle(GetAdminStatsQuery request, CancellationToken ct)
+    {
+        var students = await studentRepository.GetAllWithEnrollmentsAsync(ct);
+        var totalStudents = students.Count;
+
+        var totalEnrollments = students.Sum(s => s.Enrollments.Count);
+
+        var avgCredits = totalStudents > 0
+            ? students.Average(s => s.Enrollments.Sum(e => e.Subject?.Credits ?? 3))
+            : 0;
+
+        var subjects = await subjectRepository.GetAllWithProfessorsAsync(ct);
+
+        var enrollmentCounts = students
+            .SelectMany(s => s.Enrollments)
+            .GroupBy(e => e.SubjectId)
+            .ToDictionary(g => g.Key, g => g.Count());
+
+        var subjectStats = subjects
+            .Select(s => new SubjectStatsDto(
+                s.Id,
+                s.Name,
+                s.Professor?.Name ?? "Sin profesor",
+                enrollmentCounts.GetValueOrDefault(s.Id, 0)))
+            .OrderByDescending(s => s.EnrollmentCount)
+            .ToList();
+
+        var mostPopular = subjectStats.FirstOrDefault();
+
+        return new AdminStatsDto(
+            totalStudents,
+            totalEnrollments,
+            Math.Round(avgCredits, 1),
+            mostPopular,
+            subjectStats);
+    }
+}

src/frontend/src/app/features/admin/pages/admin-dashboard/admin-dashboard.component.ts

@@ -0,0 +1,448 @@
+import { Component, inject, signal, OnInit } from '@angular/core';
+import { RouterLink } from '@angular/router';
+import { Apollo, gql } from 'apollo-angular';
+import { MatIconModule } from '@angular/material/icon';
+import { MatButtonModule } from '@angular/material/button';
+import { MatProgressSpinnerModule } from '@angular/material/progress-spinner';
+import { AuthService } from '@core/services/auth.service';
+
+const GET_ADMIN_STATS = gql`
+  query GetAdminStats {
+    adminStats {
+      totalStudents
+      totalEnrollments
+      averageCreditsPerStudent
+      mostPopularSubject {
+        subjectId
+        subjectName
+        professorName
+        enrollmentCount
+      }
+      subjectStats {
+        subjectId
+        subjectName
+        professorName
+        enrollmentCount
+      }
+    }
+  }
+`;
+
+interface SubjectStats {
+  subjectId: number;
+  subjectName: string;
+  professorName: string;
+  enrollmentCount: number;
+}
+
+interface AdminStats {
+  totalStudents: number;
+  totalEnrollments: number;
+  averageCreditsPerStudent: number;
+  mostPopularSubject: SubjectStats | null;
+  subjectStats: SubjectStats[];
+}
+
+@Component({
+  selector: 'app-admin-dashboard',
+  standalone: true,
+  imports: [RouterLink, MatIconModule, MatButtonModule, MatProgressSpinnerModule],
+  template: `
+    <div class="admin-dashboard">
+      @if (loading()) {
+        <div class="loading-container">
+          <mat-spinner diameter="48"></mat-spinner>
+          <p>Cargando estadisticas...</p>
+        </div>
+      } @else if (error()) {
+        <div class="error-container">
+          <mat-icon>error_outline</mat-icon>
+          <h2>Error al cargar datos</h2>
+          <p>{{ error() }}</p>
+          <button class="btn btn-primary" (click)="loadStats()">
+            <mat-icon>refresh</mat-icon>
+            Reintentar
+          </button>
+        </div>
+      } @else if (stats()) {
+        <header class="admin-header">
+          <div class="welcome">
+            <h1>Panel de Administracion</h1>
+            <p>Bienvenido, {{ authService.user()?.username }}</p>
+          </div>
+        </header>
+
+        <div class="stats-grid">
+          <div class="stat-card primary">
+            <mat-icon>people</mat-icon>
+            <div class="stat-content">
+              <span class="stat-value">{{ stats()!.totalStudents }}</span>
+              <span class="stat-label">Estudiantes</span>
+            </div>
+          </div>
+
+          <div class="stat-card success">
+            <mat-icon>school</mat-icon>
+            <div class="stat-content">
+              <span class="stat-value">{{ stats()!.totalEnrollments }}</span>
+              <span class="stat-label">Inscripciones</span>
+            </div>
+          </div>
+
+          <div class="stat-card info">
+            <mat-icon>trending_up</mat-icon>
+            <div class="stat-content">
+              <span class="stat-value">{{ stats()!.averageCreditsPerStudent }}</span>
+              <span class="stat-label">Creditos Promedio</span>
+            </div>
+          </div>
+
+          @if (stats()!.mostPopularSubject) {
+            <div class="stat-card warning">
+              <mat-icon>star</mat-icon>
+              <div class="stat-content">
+                <span class="stat-value">{{ stats()!.mostPopularSubject!.subjectName }}</span>
+                <span class="stat-label">Materia mas popular ({{ stats()!.mostPopularSubject!.enrollmentCount }} inscritos)</span>
+              </div>
+            </div>
+          }
+        </div>
+
+        <div class="dashboard-grid">
+          <section class="card actions-card">
+            <div class="card-header">
+              <h2>
+                <mat-icon>flash_on</mat-icon>
+                Acciones Rapidas
+              </h2>
+            </div>
+            <div class="actions-list">
+              <a routerLink="/students" class="action-btn">
+                <mat-icon>group</mat-icon>
+                <div>
+                  <span>Gestionar Estudiantes</span>
+                  <small>Ver, crear, editar y eliminar estudiantes</small>
+                </div>
+              </a>
+              <a routerLink="/students/new" class="action-btn">
+                <mat-icon>person_add</mat-icon>
+                <div>
+                  <span>Nuevo Estudiante</span>
+                  <small>Registrar un nuevo estudiante</small>
+                </div>
+              </a>
+            </div>
+          </section>
+
+          <section class="card subjects-card">
+            <div class="card-header">
+              <h2>
+                <mat-icon>bar_chart</mat-icon>
+                Inscripciones por Materia
+              </h2>
+            </div>
+            <div class="subjects-list">
+              @for (subject of stats()!.subjectStats; track subject.subjectId) {
+                <div class="subject-item">
+                  <div class="subject-info">
+                    <span class="subject-name">{{ subject.subjectName }}</span>
+                    <span class="professor">Prof. {{ subject.professorName }}</span>
+                  </div>
+                  <div class="enrollment-bar">
+                    <div
+                      class="bar-fill"
+                      [style.width.%]="getBarWidth(subject.enrollmentCount)">
+                    </div>
+                    <span class="enrollment-count">{{ subject.enrollmentCount }}</span>
+                  </div>
+                </div>
+              }
+            </div>
+          </section>
+        </div>
+      }
+    </div>
+  `,
+  styles: [`
+    .admin-dashboard {
+      max-width: 1200px;
+      margin: 0 auto;
+    }
+
+    .loading-container, .error-container {
+      display: flex;
+      flex-direction: column;
+      align-items: center;
+      justify-content: center;
+      min-height: 400px;
+      gap: 1rem;
+      text-align: center;
+    }
+
+    .error-container mat-icon {
+      font-size: 64px;
+      width: 64px;
+      height: 64px;
+      color: var(--error);
+    }
+
+    .admin-header {
+      margin-bottom: 2rem;
+      padding: 1.5rem;
+      background: linear-gradient(135deg, #1e3a8a 0%, #3b82f6 100%);
+      border-radius: 1rem;
+      color: white;
+    }
+
+    .admin-header h1 {
+      margin: 0 0 0.25rem;
+      font-size: 1.75rem;
+      font-weight: 600;
+    }
+
+    .admin-header p {
+      margin: 0;
+      opacity: 0.9;
+    }
+
+    .stats-grid {
+      display: grid;
+      grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
+      gap: 1rem;
+      margin-bottom: 2rem;
+    }
+
+    .stat-card {
+      display: flex;
+      align-items: center;
+      gap: 1rem;
+      padding: 1.25rem;
+      background: white;
+      border-radius: 1rem;
+      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
+    }
+
+    .stat-card mat-icon {
+      font-size: 40px;
+      width: 40px;
+      height: 40px;
+      padding: 0.75rem;
+      border-radius: 0.75rem;
+    }
+
+    .stat-card.primary mat-icon {
+      background: rgba(59, 130, 246, 0.1);
+      color: #3b82f6;
+    }
+
+    .stat-card.success mat-icon {
+      background: rgba(34, 197, 94, 0.1);
+      color: #22c55e;
+    }
+
+    .stat-card.info mat-icon {
+      background: rgba(99, 102, 241, 0.1);
+      color: #6366f1;
+    }
+
+    .stat-card.warning mat-icon {
+      background: rgba(245, 158, 11, 0.1);
+      color: #f59e0b;
+    }
+
+    .stat-content {
+      display: flex;
+      flex-direction: column;
+    }
+
+    .stat-value {
+      font-size: 1.5rem;
+      font-weight: 700;
+      color: var(--text-primary);
+    }
+
+    .stat-label {
+      font-size: 0.8125rem;
+      color: var(--text-secondary);
+    }
+
+    .dashboard-grid {
+      display: grid;
+      gap: 1.5rem;
+      grid-template-columns: 1fr;
+    }
+
+    @media (min-width: 768px) {
+      .dashboard-grid {
+        grid-template-columns: 1fr 2fr;
+      }
+    }
+
+    .card {
+      background: white;
+      border-radius: 1rem;
+      padding: 1.5rem;
+      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
+    }
+
+    .card-header {
+      display: flex;
+      align-items: center;
+      justify-content: space-between;
+      margin-bottom: 1rem;
+    }
+
+    .card-header h2 {
+      display: flex;
+      align-items: center;
+      gap: 0.5rem;
+      margin: 0;
+      font-size: 1.125rem;
+      font-weight: 600;
+    }
+
+    .card-header mat-icon {
+      color: var(--accent);
+    }
+
+    .actions-list {
+      display: flex;
+      flex-direction: column;
+      gap: 0.75rem;
+    }
+
+    .action-btn {
+      display: flex;
+      align-items: center;
+      gap: 1rem;
+      padding: 1rem;
+      background: var(--bg-secondary);
+      border-radius: 0.75rem;
+      text-decoration: none;
+      color: inherit;
+      transition: all 0.2s;
+    }
+
+    .action-btn:hover {
+      background: var(--border-light);
+      transform: translateX(4px);
+    }
+
+    .action-btn mat-icon {
+      color: var(--accent);
+    }
+
+    .action-btn div {
+      display: flex;
+      flex-direction: column;
+    }
+
+    .action-btn span {
+      font-weight: 500;
+    }
+
+    .action-btn small {
+      font-size: 0.75rem;
+      color: var(--text-secondary);
+    }
+
+    .subjects-list {
+      display: flex;
+      flex-direction: column;
+      gap: 0.75rem;
+    }
+
+    .subject-item {
+      display: flex;
+      justify-content: space-between;
+      align-items: center;
+      padding: 0.75rem 1rem;
+      background: var(--bg-secondary);
+      border-radius: 0.5rem;
+    }
+
+    .subject-info {
+      display: flex;
+      flex-direction: column;
+      gap: 0.125rem;
+    }
+
+    .subject-name {
+      font-weight: 500;
+      font-size: 0.9375rem;
+    }
+
+    .professor {
+      font-size: 0.75rem;
+      color: var(--text-secondary);
+    }
+
+    .enrollment-bar {
+      display: flex;
+      align-items: center;
+      gap: 0.5rem;
+      min-width: 100px;
+    }
+
+    .bar-fill {
+      height: 8px;
+      background: linear-gradient(90deg, #3b82f6, #6366f1);
+      border-radius: 4px;
+      min-width: 4px;
+      transition: width 0.3s ease;
+    }
+
+    .enrollment-count {
+      font-size: 0.875rem;
+      font-weight: 600;
+      color: var(--text-secondary);
+      min-width: 20px;
+      text-align: right;
+    }
+  `]
+})
+export class AdminDashboardComponent implements OnInit {
+  private apollo = inject(Apollo);
+  authService = inject(AuthService);
+
+  stats = signal<AdminStats | null>(null);
+  loading = signal(true);
+  error = signal<string | null>(null);
+
+  private maxEnrollments = 0;
+
+  ngOnInit(): void {
+    this.loadStats();
+  }
+
+  loadStats(): void {
+    this.loading.set(true);
+    this.error.set(null);
+
+    this.apollo
+      .query<{ adminStats: AdminStats }>({
+        query: GET_ADMIN_STATS,
+        fetchPolicy: 'network-only',
+      })
+      .subscribe({
+        next: (result) => {
+          if (result.data?.adminStats) {
+            this.stats.set(result.data.adminStats);
+            this.maxEnrollments = Math.max(
+              ...result.data.adminStats.subjectStats.map(s => s.enrollmentCount),
+              1
+            );
+          }
+          this.loading.set(false);
+        },
+        error: (err) => {
+          this.error.set(err.message || 'Error al cargar estadisticas');
+          this.loading.set(false);
+        },
+      });
+  }
+
+  getBarWidth(count: number): number {
+    return (count / this.maxEnrollments) * 100;
+  }
+}