Prevent task starting and completion without assigned it staff

lib/providers/tasks_provider.dart

@@ -1102,6 +1102,36 @@ class TasksController {
     }
 
     if (status == 'completed') {
+      // Check for IT staff assignment
+      final assignmentRows = await _client
+          .from('task_assignments')
+          .select('user_id')
+          .eq('task_id', taskId);
+      final assignedUserIds = (assignmentRows as List)
+          .map((row) => row['user_id']?.toString())
+          .whereType<String>()
+          .where((id) => id.isNotEmpty)
+          .toSet()
+          .toList();
+      if (assignedUserIds.isEmpty) {
+        throw Exception(
+          'Assign at least one IT Staff before completing this task.',
+        );
+      }
+
+      final itStaffRows = await _client
+          .from('profiles')
+          .select('id')
+          .inFilter('id', assignedUserIds)
+          .eq('role', 'it_staff');
+      final hasItStaff = (itStaffRows as List).isNotEmpty;
+      if (!hasItStaff) {
+        throw Exception(
+          'Assign at least one IT Staff before completing this task.',
+        );
+      }
+
+      // Check required fields
       try {
         final rt = taskRow['request_type'];
         final rc = taskRow['request_category'];

lib/screens/tasks/task_detail_screen.dart

@@ -3503,12 +3503,8 @@ class _TaskDetailScreenState extends ConsumerState<TaskDetailScreen>
       return chip;
     }
 
-    final statusOptions = _statusOptions.where((status) {
-      if (status == 'in_progress' && !hasAssignedItStaff) {
-        return false;
-      }
-      return true;
-    }).toList();
+    // Show all status options - validation happens on selection
+    final statusOptions = _statusOptions;
 
     return PopupMenuButton<String>(
       onSelected: (value) async {
@@ -3606,6 +3602,16 @@ class _TaskDetailScreenState extends ConsumerState<TaskDetailScreen>
           return;
         }
 
+        // Validate IT staff assignment before starting or completing
+        if ((value == 'in_progress' || value == 'completed') &&
+            !hasAssignedItStaff) {
+          showWarningSnackBar(
+            context,
+            'Please assign at least one IT Staff member before ${value == 'in_progress' ? 'starting' : 'completing'} this task.',
+          );
+          return;
+        }
+
         // Update DB only — Supabase realtime stream will emit the
         // updated task list, so explicit invalidation here causes a
         // visible loading/refresh and is unnecessary.