Fix: replace collapsed search icon with X when search is active, hide FAB/pagination while searching

frontend/lib/ui/screens/students/students_screen.dart

@@ -481,7 +481,7 @@ class _StudentsScreenState extends ConsumerState<StudentsScreen> {
     return Scaffold(
       backgroundColor: Colors.transparent,
       floatingActionButtonLocation: FloatingActionButtonLocation.endFloat,
-      floatingActionButton: (widget.userRole == 'teacher' || _showMultiSelect) ? null : FloatingActionButton(
+      floatingActionButton: (widget.userRole == 'teacher' || _showMultiSelect || _searchFocusNode.hasFocus) ? null : FloatingActionButton(
         heroTag: 'add_student_fab',
         backgroundColor: AppColors.primaryGreen,
         foregroundColor: Colors.white,
@@ -539,9 +539,10 @@ class _StudentsScreenState extends ConsumerState<StudentsScreen> {
             ),
 
             // ── Pagination ──
-            pageAsync.maybeWhen(
-              data:   (page) => _buildPagination(query, page),
-              orElse: () => const SizedBox.shrink(),
+            if (!_searchFocusNode.hasFocus)
+              pageAsync.maybeWhen(
+                data:   (page) => _buildPagination(query, page),
+                orElse: () => const SizedBox.shrink(),
               ),
               ],
             ),

frontend/lib/ui/shared/inputs/app_search_bar.dart

@@ -199,6 +199,17 @@ class _AppSearchBarState extends ConsumerState<AppSearchBar> {
   @override
   Widget build(BuildContext context) {
     if (!_isExpanded && widget.collapsible) {
+      if (_hasText) {
+        return IconButton(
+          onPressed: () {
+            _controller.clear();
+            widget.onChanged?.call('');
+            if (widget.onSubmitted != null) widget.onSubmitted!('');
+          },
+          icon: const Icon(Icons.close, size: 28, color: Colors.redAccent),
+          tooltip: 'Clear search',
+        );
+      }
       return IconButton(
         onPressed: () {
           setState(() => _isExpanded = true);