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>

backend/src/routes/public/mitra.chat.routes.js

@@ -3,6 +3,7 @@ import { getMitraById } from '../../services/mitra.service.js'
 import { acceptPairingRequest, declinePairingRequest, getSessionStatus, getPendingRequestsForMitra } from '../../services/pairing.service.js'
 import { getActiveSessionsByMitra, getActiveSessionsByMitraWithUnread, endSession, getMitraHistory } from '../../services/session.service.js'
 import { respondToExtension } from '../../services/extension.service.js'
+import { getRecentRequestsForMitra } from '../../services/mitra-activity.service.js'
 import { EndedBy, UserType } from '../../constants.js'
 
 const resolveMitra = async (request, reply) => {
@@ -35,6 +36,15 @@ export const mitraChatRoutes = async (app) => {
     return reply.send({ success: true, data: requests })
   })
 
+  // Phase 3.5: Get last N (max 20) chat requests for this mitra (any status, pending pinned first)
+  app.get('/recent', { preHandler: [authenticate, resolveMitra] }, async (request, reply) => {
+    const { limit } = request.query
+    const items = await getRecentRequestsForMitra(request.mitra.id, {
+      limit: limit ? parseInt(limit) : 20,
+    })
+    return reply.send({ success: true, data: items })
+  })
+
   // Check if a session is still pending acceptance (for notification validation)
   app.get('/:sessionId/status', { preHandler: [authenticate, resolveMitra] }, async (request, reply) => {
     const session = await getSessionStatus(request.params.sessionId)