feat: gestion de materias por rol - Bedelia, Docente y Alumno

- Nuevo modelo StudentEnrollment (tabla student_enrollments)
  con inscripcion unica por alumno/comision, estado y notas

- Migracion automatica en init_db.py (CREATE TABLE IF NOT EXISTS)

- Rutas /admin/commissions/ para Bedelia y Admin:
  listado con filtros, detalle, asignar docente,
  inscribir/dar de baja alumnos, cambiar estado

- Blueprint my_subjects_bp en /mis-materias:
  Docente ve solo sus comisiones asignadas
  Alumno ve solo sus inscripciones activas
  Admin/Bedelia ven todo

- Templates: admin/commissions/list.html, detail.html
            my_subjects/list.html, detail.html

- Navbar actualizado por rol:
  Docente y Alumno: 'Mis Materias'
  Bedelia y Admin: 'Gestion de Comisiones'

app/routes/my_subjects.py

@@ -0,0 +1,126 @@
+from flask import Blueprint, render_template, abort
+from flask_login import login_required, current_user
+from app import db
+from app.models.subject import Commission
+from app.models.enrollment import StudentEnrollment
+from app.models.classroom import Classroom
+
+my_subjects_bp = Blueprint('my_subjects', __name__, url_prefix='/mis-materias')
+
+
+@my_subjects_bp.route('/')
+@login_required
+def my_subjects_list():
+    """Show the commissions assigned to the current user (teacher or student)."""
+    role = current_user.get_institutional_role()
+
+    commissions = []
+
+    if role in ['admin', 'bedelia']:
+        # Admin/Bedelia: see all active commissions
+        commissions = (
+            Commission.query
+            .filter_by(active=True)
+            .order_by(Commission.year.desc(), Commission.semester.asc(), Commission.code.asc())
+            .all()
+        )
+        view_mode = 'all'
+
+    elif role == 'docente':
+        # Teacher: only commissions where they are assigned as teacher
+        commissions = (
+            Commission.query
+            .filter_by(teacher_id=current_user.id, active=True)
+            .order_by(Commission.year.desc(), Commission.semester.asc(), Commission.code.asc())
+            .all()
+        )
+        view_mode = 'teacher'
+
+    elif role == 'alumno':
+        # Student: only commissions where they are enrolled
+        enrollments = (
+            StudentEnrollment.query
+            .filter_by(student_id=current_user.id, status='activo')
+            .all()
+        )
+        commission_ids = [e.commission_id for e in enrollments]
+        commissions = (
+            Commission.query
+            .filter(Commission.id.in_(commission_ids), Commission.active == True)
+            .order_by(Commission.year.desc(), Commission.semester.asc(), Commission.code.asc())
+            .all()
+        )
+        view_mode = 'student'
+    else:
+        commissions = []
+        view_mode = 'none'
+
+    return render_template(
+        'my_subjects/list.html',
+        commissions=commissions,
+        view_mode=view_mode,
+        role=role
+    )
+
+
+@my_subjects_bp.route('/<int:commission_id>')
+@login_required
+def my_subject_detail(commission_id):
+    """Detail view of a single commission for the current user."""
+    role = current_user.get_institutional_role()
+    commission = Commission.query.get_or_404(commission_id)
+
+    # Access control: make sure the user is allowed to see this commission
+    if role in ['admin', 'bedelia']:
+        pass  # full access
+    elif role == 'docente':
+        if commission.teacher_id != current_user.id:
+            abort(403)
+    elif role == 'alumno':
+        enrollment = StudentEnrollment.query.filter_by(
+            student_id=current_user.id,
+            commission_id=commission_id
+        ).first()
+        if not enrollment:
+            abort(403)
+    else:
+        abort(403)
+
+    # Get enrolled students (visible to teachers and admin/bedelia)
+    enrollments = []
+    if role in ['admin', 'bedelia', 'docente']:
+        enrollments = (
+            StudentEnrollment.query
+            .filter_by(commission_id=commission_id)
+            .order_by(StudentEnrollment.enrolled_at.asc())
+            .all()
+        )
+
+    # Try to get classroom info from reservations linked to this commission
+    from app.models.reservation import Reservation
+    from sqlalchemy import func
+    from datetime import datetime
+
+    # Recent or upcoming reservation linked to this commission
+    recent_reservation = (
+        Reservation.query
+        .filter(
+            Reservation.commission_id == commission_id,
+            Reservation.start_time >= datetime.utcnow()
+        )
+        .order_by(Reservation.start_time.asc())
+        .first()
+    )
+
+    classroom = None
+    if recent_reservation and recent_reservation.classroom_id:
+        classroom = Classroom.query.get(recent_reservation.classroom_id)
+
+    return render_template(
+        'my_subjects/detail.html',
+        commission=commission,
+        enrollments=enrollments,
+        classroom=classroom,
+        recent_reservation=recent_reservation,
+        role=role
+    )