Phase 4 Stage 6: chat-room countdown UX + voice-call mode pill

Customer chat screen:
- Voice-call header pill (mode == 'call' renders accent-colored pill;
  chat mode renders no pill).
- HaloSnackbar fires once per session at 180s remaining ('sisa 3 menit
  lagi ya 🤍'), driven by the backend session_warning WS event.
- Last-2-min danger styling: timer pill flips to HaloTokens.danger +
  bold JetBrainsMono when remaining <= 120s.
- Floating ChatExpiredBanner widget injected above the input bar when
  remaining hits 0 in closing-grace state. perpanjang -> existing
  pricing bottom sheet.
- pricing_bottom_sheet.dart rewritten to the 5-option layout with
  chat|call mode toggle (mirrors duration-pick from Stage 3).

Mitra chat screen: voice-call header pill only (no countdown UX per PRD).

Backend:
- session.service.js getSessionById JOINs payment_sessions so mode +
  expires_at ship in /api/shared/chat/:id/info.
- session-timer.service.js onThreeMinuteWarning now emits expires_at +
  remaining_seconds for client resync.
- Dev-only POST /internal/_test/force-session-expires-at clears the
  3-min flag, reschedules the timer, and broadcasts WS resync. Lets
  the Maestro flow drive 175s -> 90s -> 0s without waiting live.

New chatRemainingSeconds StreamProvider derived from expiresAt, fed by
session_warning / session_timer / session_expired resync messages
(plan referenced a secondsLeftProvider that didn't actually exist).

Maestro 06_chat_countdown.yaml + force_session_expires_at.js helper.

Out of scope: meet.google.com URL launching - url_launcher isn't a
client_app dependency and message bubbles render plain Text. Defer.

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

mitra_app/lib/features/chat/screens/mitra_chat_screen.dart

@@ -13,6 +13,9 @@ import '../../../core/constants.dart';
 const _kUserBubbleColor = Color(0xFFD4929A);
 const _kBannerColor = Color(0xFFC4868F);
 const _kAccentPink = Color(0xFFBE7C8A);
+// Phase 4 — voice-call mode badge background. Mirrors `HaloTokens.accent`
+// from the customer app palette so both apps render the same pill color.
+const _kVoiceCallPillColor = Color(0xFFF7B26A);
 
 class MitraChatScreen extends ConsumerStatefulWidget {
   final String sessionId;
@@ -117,7 +120,23 @@ class _MitraChatScreenState extends ConsumerState<MitraChatScreen> {
           icon: const Icon(Icons.chevron_left, size: 28),
           onPressed: () => context.pop(),
         ),
-        title: Text(widget.customerName),
+        title: Row(
+          mainAxisSize: MainAxisSize.min,
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: [
+            Flexible(
+              child: Text(
+                widget.customerName,
+                overflow: TextOverflow.ellipsis,
+              ),
+            ),
+            if (chatState is MitraChatConnectedData &&
+                chatState.mode == SessionMode.call) ...[
+              const SizedBox(width: 8),
+              _buildVoiceCallPill(),
+            ],
+          ],
+        ),
         actions: [
           if (chatState is MitraChatConnectedData) _buildTopicToggle(chatState),
           if (chatState is MitraChatConnectedData && chatState.remainingSeconds != null)
@@ -145,6 +164,24 @@ class _MitraChatScreenState extends ConsumerState<MitraChatScreen> {
     );
   }
 
+  Widget _buildVoiceCallPill() {
+    return Container(
+      padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 3),
+      decoration: const BoxDecoration(
+        color: _kVoiceCallPillColor,
+        borderRadius: BorderRadius.all(Radius.circular(9999)),
+      ),
+      child: const Text(
+        '📞 Voice Call',
+        style: TextStyle(
+          fontSize: 11,
+          fontWeight: FontWeight.w600,
+          color: Colors.white,
+        ),
+      ),
+    );
+  }
+
   Widget _buildSensitivityHeader() {
     const theme = SensitivityTheme.sensitive;
     return Container(