Allow task completion even if signatories are still empty, put an indicator for completed tasks with incomplete details.

lib/models/task.dart

@@ -53,6 +53,19 @@ class Task {
   // JSON serialized rich text for action taken (Quill Delta JSON encoded)
   final String? actionTaken;
 
+  /// Helper that indicates whether a completed task still has missing
+  /// metadata such as signatories or action details.  The parameter is used
+  /// by UI to surface a warning icon/banner when a task has been closed but
+  /// the user skipped filling out all fields.
+  bool get hasIncompleteDetails {
+    if (status != 'completed') return false;
+    bool empty(String? v) => v == null || v.trim().isEmpty;
+    return empty(requestedBy) ||
+        empty(notedBy) ||
+        empty(receivedBy) ||
+        empty(actionTaken);
+  }
+
   factory Task.fromMap(Map<String, dynamic> map) {
     return Task(
       id: map['id'] as String,