feat(students): add guidance notes on enrollment downgrading in edit student modal

frontend/lib/ui/screens/students/widgets/edit_enrollment_modal.dart

@@ -573,24 +573,41 @@ class _EditEnrollmentModalState extends ConsumerState<EditEnrollmentModal> {
                   ),
                   borderRadius: BorderRadius.circular(AppSizes.radiusMedium),
                 ),
-                child: Row(
+                child: Column(
                   crossAxisAlignment: CrossAxisAlignment.start,
                   children: [
-                    const Icon(
+                    Row(
-                      Icons.error_outline,
+                      crossAxisAlignment: CrossAxisAlignment.start,
-                      color: AppColors.error,
+                      children: [
-                      size: 20,
+                        const Icon(
-                    ),
+                          Icons.error_outline,
-                    const SizedBox(width: 8),
-                    Expanded(
-                      child: Text(
-                        _errorMessage!,
-                        style: const TextStyle(
                           color: AppColors.error,
-                          fontSize: 14,
+                          size: 20,
+                        ),
+                        const SizedBox(width: 8),
+                        Expanded(
+                          child: Text(
+                            _errorMessage!,
+                            style: const TextStyle(
+                              color: AppColors.error,
+                              fontSize: 13,
+                              fontWeight: FontWeight.w500,
+                            ),
+                          ),
+                        ),
+                      ],
+                    ),
+                    if (_errorMessage!.toLowerCase().contains('downgrade') ||
+                        _errorMessage!.toLowerCase().contains('lower')) ...[
+                      const SizedBox(height: 8),
+                      Text(
+                        'Tip: To correct a grade level or downgrade a student, delete the higher enrollment record(s) first from the Enrollments tab.',
+                        style: TextStyle(
+                          fontSize: 12,
+                          color: Theme.of(context).colorScheme.onSurface.withValues(alpha: 0.75),
                         ),
                       ),
-                    ),
+                    ],
                   ],
                 ),
               ),

frontend/lib/ui/screens/students/widgets/edit_student_modal.dart

@@ -865,7 +865,63 @@ class _EditStudentModalState extends ConsumerState<EditStudentModal> {
                   ],
                 ),
               ],
-              const SizedBox(height: 16),
+              const SizedBox(height: 14),
+
+              // ── Downgrade / Correction Guidance Note ──
+              Container(
+                padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 10),
+                decoration: BoxDecoration(
+                  color: isDark
+                      ? Colors.blue.withValues(alpha: 0.12)
+                      : Colors.blue.shade50,
+                  borderRadius: BorderRadius.circular(10),
+                  border: Border.all(
+                    color: isDark
+                        ? Colors.blue.withValues(alpha: 0.3)
+                        : Colors.blue.shade200,
+                  ),
+                ),
+                child: Row(
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: [
+                    Icon(
+                      Icons.info_outline_rounded,
+                      size: 18,
+                      color: isDark ? Colors.blue.shade300 : Colors.blue.shade700,
+                    ),
+                    const SizedBox(width: 10),
+                    Expanded(
+                      child: RichText(
+                        text: TextSpan(
+                          style: TextStyle(
+                            fontSize: 12,
+                            height: 1.4,
+                            color: isDark
+                                ? AppColors.darkTextPrimary
+                                : const Color(0xFF1E293B),
+                          ),
+                          children: [
+                            TextSpan(
+                              text: 'Note on Downgrading: ',
+                              style: TextStyle(
+                                fontWeight: FontWeight.bold,
+                                color: isDark
+                                    ? Colors.blue.shade300
+                                    : Colors.blue.shade700,
+                              ),
+                            ),
+                            const TextSpan(
+                              text:
+                                  'To correct a mistake or downgrade a student\'s grade level, delete the higher enrollment record(s) first to bypass downgrading restrictions.',
+                            ),
+                          ],
+                        ),
+                      ),
+                    ),
+                  ],
+                ),
+              ),
+              const SizedBox(height: 14),
               if (sorted.isEmpty)
                 Container(
                   padding: const EdgeInsets.all(32),