Phase 3: closing-overlay fix + goodbye-composer dedupe

Customer chat refreshSessionStatus now clears sessionExpired carryover so the
goodbye composer renders correctly when re-opening a closing session from
history. Backend /api/shared/chat/:id/info returns goodbye_submitted_by_me;
both apps suppress the composer for the side that has already submitted and
render an awaiting-banner view instead.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

mitra_app/lib/core/chat/mitra_chat_notifier.dart

@@ -29,6 +29,7 @@ class MitraChatConnectedData extends MitraChatData {
   final int? remainingSeconds;
   final bool sessionExpired;
   final bool sessionClosing;
+  final bool goodbyeSubmitted;
   final Map<String, dynamic>? extensionRequest;
   final TopicSensitivity topicSensitivity;
 
@@ -38,6 +39,7 @@ class MitraChatConnectedData extends MitraChatData {
     this.remainingSeconds,
     this.sessionExpired = false,
     this.sessionClosing = false,
+    this.goodbyeSubmitted = false,
     this.extensionRequest,
     this.topicSensitivity = TopicSensitivity.regular,
   });
@@ -48,6 +50,7 @@ class MitraChatConnectedData extends MitraChatData {
     int? remainingSeconds,
     bool? sessionExpired,
     bool? sessionClosing,
+    bool? goodbyeSubmitted,
     Map<String, dynamic>? extensionRequest,
     bool clearExtensionRequest = false,
     TopicSensitivity? topicSensitivity,
@@ -58,6 +61,7 @@ class MitraChatConnectedData extends MitraChatData {
       remainingSeconds: remainingSeconds ?? this.remainingSeconds,
       sessionExpired: sessionExpired ?? this.sessionExpired,
       sessionClosing: sessionClosing ?? this.sessionClosing,
+      goodbyeSubmitted: goodbyeSubmitted ?? this.goodbyeSubmitted,
       extensionRequest: clearExtensionRequest ? null : (extensionRequest ?? this.extensionRequest),
       topicSensitivity: topicSensitivity ?? this.topicSensitivity,
     );
@@ -124,6 +128,7 @@ class MitraChat extends _$MitraChat {
       }
 
       final isClosing = sessionStatus == SessionStatus.closing;
+      final goodbyeSubmittedByMe = sessionData?['goodbye_submitted_by_me'] as bool? ?? false;
       final sessionTopic = TopicSensitivity.fromString(sessionData?['topic_sensitivity'] as String?);
 
       final response = await _apiClient.get('/api/shared/chat/$sessionId/messages');
@@ -162,7 +167,12 @@ class MitraChat extends _$MitraChat {
         'session_id': sessionId,
       }));
 
-      state = MitraChatConnectedData(messages: messages, sessionClosing: isClosing, topicSensitivity: sessionTopic);
+      state = MitraChatConnectedData(
+        messages: messages,
+        sessionClosing: isClosing,
+        goodbyeSubmitted: goodbyeSubmittedByMe,
+        topicSensitivity: sessionTopic,
+      );
     } catch (e) {
       state = const MitraChatErrorData('Gagal terhubung ke chat.');
     }