Phase 3.5: Mitra Chat Request History (backend route + mitra app screens)

Replaces the home-screen pending-requests banner with a "Riwayat
Permintaan" CTA that opens a list of the mitra's last 20 chat requests
(any status). Pending rows pin to the top; non-pending rows open a
read-only detail screen with a "Lihat percakapan" CTA on accepted rows.

Backend:
- New service `getRecentRequestsForMitra(mitraId, { limit })` capped at
  20, pending pinned via `(response IS NULL AND status='pending_acceptance')
  DESC`. Customer call_name returned verbatim, with `'Anonim'` only as
  null-safety fallback (no anonymity-flag masking — see project memory).
- New route `GET /api/mitra/chat-requests/recent`. Strictly per-mitra
  scoped via the existing `resolveMitra` preHandler.

Mitra app:
- New `RequestResponse` enum in core/constants.dart.
- New Riverpod notifier `requestHistoryProvider` (AsyncValue<List<...>>,
  keepAlive) — pull-to-refresh + screen-mount fetch only, no WS.
- Two new screens (history list + detail) and two new GoRoutes.
- Home screen: `_PendingRequestsBanner` removed → `_RequestHistoryButton`
  Card with red count badge. Live count comes from the existing
  chatRequestProvider so nothing changes about the WS-driven badge math.

Plan + acceptance criteria in requirement/phase3.5-plan.md. flutter
analyze clean (zero new issues). Backend smoke-tested against real DB.
Real-device E2E pending.

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

mitra_app/lib/features/chat/utils/request_status_label.dart

@@ -0,0 +1,77 @@
+import 'package:flutter/material.dart';
+
+import '../../../core/constants.dart';
+import '../models/request_history_entry.dart';
+
+class RequestStatusLabel {
+  final String label;
+  final Color background;
+  final Color foreground;
+  const RequestStatusLabel(this.label, this.background, this.foreground);
+}
+
+RequestStatusLabel labelFor(RequestHistoryEntry entry) {
+  if (entry.isPending) {
+    return RequestStatusLabel(
+      'Menunggu respon',
+      Colors.amber.shade100,
+      Colors.amber.shade900,
+    );
+  }
+  switch (entry.response) {
+    case RequestResponse.accepted:
+      return RequestStatusLabel(
+        'Diterima',
+        Colors.green.shade100,
+        Colors.green.shade900,
+      );
+    case RequestResponse.declined:
+      return RequestStatusLabel(
+        'Ditolak',
+        Colors.grey.shade300,
+        Colors.grey.shade800,
+      );
+    case RequestResponse.missed:
+      return RequestStatusLabel(
+        'Terlewat',
+        Colors.grey.shade300,
+        Colors.grey.shade800,
+      );
+    case RequestResponse.ignored:
+      if (entry.sessionStatus == SessionStatus.cancelled) {
+        return RequestStatusLabel(
+          'Dibatalkan',
+          Colors.grey.shade300,
+          Colors.grey.shade800,
+        );
+      }
+      return RequestStatusLabel(
+        'Kedaluwarsa',
+        Colors.grey.shade300,
+        Colors.grey.shade800,
+      );
+    case null:
+      // Non-pending null (session moved past pending_acceptance without a logged response)
+      return RequestStatusLabel(
+        'Kedaluwarsa',
+        Colors.grey.shade300,
+        Colors.grey.shade800,
+      );
+  }
+}
+
+String formatRelative(DateTime when) {
+  final now = DateTime.now();
+  final diff = now.difference(when);
+  if (diff.inSeconds < 60) return 'Baru saja';
+  if (diff.inMinutes < 60) return '${diff.inMinutes} menit lalu';
+  if (diff.inHours < 24) return '${diff.inHours} jam lalu';
+  if (diff.inDays < 2) return 'Kemarin';
+  return '${diff.inDays} hari lalu';
+}
+
+String _two(int n) => n.toString().padLeft(2, '0');
+
+String formatAbsolute(DateTime when) {
+  return '${when.day}/${when.month}/${when.year} ${_two(when.hour)}:${_two(when.minute)}';
+}