Added validation when task type, category, signatories and action taken are empty upon completing a task

lib/providers/tasks_provider.dart

@@ -556,22 +556,56 @@ class TasksController {
     required String status,
   }) async {
     if (status == 'completed') {
-      // fetch current metadata to validate
+      // fetch current metadata to validate several required fields
       try {
         final row = await _client
             .from('tasks')
-            .select('request_type, request_category')
+            // include all columns that must be non-null/empty before completing
+            .select(
+              'request_type, request_category, requested_by, noted_by, received_by, action_taken',
+            )
             .eq('id', taskId)
             .maybeSingle();
-        final rt = row is Map ? row['request_type'] : null;
-        final rc = row is Map ? row['request_category'] : null;
-        if (rt == null || rc == null) {
+        if (row is! Map<String, dynamic>) {
+          throw Exception('Task not found');
+        }
+
+        final rt = row['request_type'];
+        final rc = row['request_category'];
+        final requested = row['requested_by'];
+        final noted = row['noted_by'];
+        final received = row['received_by'];
+        final action = row['action_taken'];
+
+        final missing = <String>[];
+        if (rt == null || (rt is String && rt.trim().isEmpty)) {
+          missing.add('request type');
+        }
+        if (rc == null || (rc is String && rc.trim().isEmpty)) {
+          missing.add('request category');
+        }
+        if (requested == null ||
+            (requested is String && requested.trim().isEmpty)) {
+          missing.add('requested by');
+        }
+        if (noted == null || (noted is String && noted.trim().isEmpty)) {
+          missing.add('noted by');
+        }
+        if (received == null ||
+            (received is String && received.trim().isEmpty)) {
+          missing.add('received by');
+        }
+        if (action == null || (action is String && action.trim().isEmpty)) {
+          missing.add('action taken');
+        }
+
+        if (missing.isNotEmpty) {
           throw Exception(
-            'Request type and category must be set before completing a task.',
+            'The following fields must be set before completing a task: ${missing.join(', ')}.',
           );
         }
       } catch (e) {
-        // rethrow so callers can handle
+        // rethrow so callers can handle (UI will display message)
         rethrow;
       }
     }

lib/screens/tasks/task_detail_screen.dart

@@ -2731,9 +2731,16 @@ class _TaskDetailScreenState extends ConsumerState<TaskDetailScreen>
         // Update DB only — Supabase realtime stream will emit the
         // updated task list, so explicit invalidation here causes a
         // visible loading/refresh and is unnecessary.
-        await ref
-            .read(tasksControllerProvider)
-            .updateTaskStatus(taskId: task.id, status: value);
+        try {
+          await ref
+              .read(tasksControllerProvider)
+              .updateTaskStatus(taskId: task.id, status: value);
+        } catch (e) {
+          // surface validation or other errors to user
+          if (mounted) {
+            showErrorSnackBar(context, e.toString());
+          }
+        }
       },
       itemBuilder: (context) => _statusOptions
           .map(