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/notifiers/request_history_notifier.dart

@@ -0,0 +1,37 @@
+import 'dart:async';
+
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+
+import '../../../core/api/api_client_provider.dart';
+import '../models/request_history_entry.dart';
+
+part 'request_history_notifier.g.dart';
+
+@Riverpod(keepAlive: true)
+class RequestHistory extends _$RequestHistory {
+  @override
+  FutureOr<List<RequestHistoryEntry>> build() async {
+    return _fetch();
+  }
+
+  Future<void> refresh() async {
+    state = const AsyncLoading();
+    state = await AsyncValue.guard(_fetch);
+  }
+
+  Future<List<RequestHistoryEntry>> _fetch() async {
+    final api = ref.read(apiClientProvider);
+    final response = await api.get('/api/mitra/chat-requests/recent');
+    final items = (response['data'] as List<dynamic>).cast<Map<String, dynamic>>();
+    return items.map(RequestHistoryEntry.fromJson).toList();
+  }
+
+  RequestHistoryEntry? findById(String notificationId) {
+    final list = state.valueOrNull;
+    if (list == null) return null;
+    for (final e in list) {
+      if (e.notificationId == notificationId) return e;
+    }
+    return null;
+  }
+}

mitra_app/lib/features/chat/notifiers/request_history_notifier.g.dart

@@ -0,0 +1,26 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'request_history_notifier.dart';
+
+// **************************************************************************
+// RiverpodGenerator
+// **************************************************************************
+
+String _$requestHistoryHash() => r'f97e75e7fa5088293c606fd3cec1ad7bd4f96480';
+
+/// See also [RequestHistory].
+@ProviderFor(RequestHistory)
+final requestHistoryProvider =
+    AsyncNotifierProvider<RequestHistory, List<RequestHistoryEntry>>.internal(
+  RequestHistory.new,
+  name: r'requestHistoryProvider',
+  debugGetCreateSourceHash: const bool.fromEnvironment('dart.vm.product')
+      ? null
+      : _$requestHistoryHash,
+  dependencies: null,
+  allTransitiveDependencies: null,
+);
+
+typedef _$RequestHistory = AsyncNotifier<List<RequestHistoryEntry>>;
+// ignore_for_file: type=lint
+// ignore_for_file: subtype_of_sealed_class, invalid_use_of_internal_member, invalid_use_of_visible_for_testing_member, deprecated_member_use_from_same_package