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>

client_app/lib/features/chat/screens/chat_screen.dart

@@ -233,15 +233,23 @@ class _ChatScreenState extends ConsumerState<ChatScreen> {
     // we mounted directly into a `closing` session (e.g. opened from history).
     // The chatProvider listener can't catch this case because it only fires on
     // transitions, not the current state at mount time.
-    final shouldShowGoodbye = closureState is ClosureShowGoodbyeData ||
-        closureState is ClosureSubmittingData ||
-        (state.sessionClosing &&
-            !state.sessionExpired &&
-            closureState is! ClosureCompleteData);
+    // Suppress when the customer has already submitted their goodbye — the
+    // session can stay in `closing` while waiting for the mitra to submit
+    // their own message or for the 5-min grace timer to auto-complete.
+    final shouldShowGoodbye = !state.goodbyeSubmitted &&
+        (closureState is ClosureShowGoodbyeData ||
+            closureState is ClosureSubmittingData ||
+            (state.sessionClosing &&
+                !state.sessionExpired &&
+                closureState is! ClosureCompleteData));
     if (shouldShowGoodbye) {
       return _buildGoodbyeView(closureState);
     }
 
+    if (state.sessionClosing && state.goodbyeSubmitted) {
+      return _buildAwaitingMitraGoodbyeView(state);
+    }
+
     if (state.sessionPaused) {
       return _buildPausedView();
     }
@@ -496,4 +504,54 @@ class _ChatScreenState extends ConsumerState<ChatScreen> {
       ),
     );
   }
+
+  Widget _buildAwaitingMitraGoodbyeView(ChatConnectedData state) {
+    return Stack(
+      children: [
+        Positioned.fill(
+          child: Container(
+            color: _kBgTint,
+            child: Image.asset(
+              'assets/images/chat_pattern.png',
+              repeat: ImageRepeat.repeat,
+              fit: BoxFit.none,
+            ),
+          ),
+        ),
+        Column(
+          children: [
+            Container(
+              width: double.infinity,
+              color: _kEndedBannerColor,
+              padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+              child: const Row(
+                children: [
+                  Icon(Icons.hourglass_top, color: _kEndedBannerText, size: 20),
+                  SizedBox(width: 8),
+                  Expanded(
+                    child: Text(
+                      'Pesan penutupmu sudah terkirim. Menunggu Bestie...',
+                      style: TextStyle(color: _kEndedBannerText, fontWeight: FontWeight.w600),
+                    ),
+                  ),
+                ],
+              ),
+            ),
+            Expanded(
+              child: ListView.builder(
+                controller: _scrollController,
+                padding: const EdgeInsets.all(16),
+                itemCount: state.messages.length,
+                itemBuilder: (context, index) {
+                  final msg = state.messages[index];
+                  final isMe = msg.senderType == UserType.customer;
+                  return _buildMessageBubble(msg, isMe);
+                },
+              ),
+            ),
+          ],
+        ),
+      ],
+    );
+  }
 }