Phase 4 checkpoint: chat-screen perf refactor + retryable blast-failure + repo-wide dispose-ref guardrail

Chat-screen performance (customer + mitra):
- Parent screens have zero `ref.watch` — only `ref.listen` for side effects
- Body extracted into its own `ConsumerStatefulWidget`; AppBar parts split
  into narrow `.select` consumers (mode, sensitivity, timer)
- Per-second timer ticks routed to dedicated providers
  (`chatRemainingSecondsProvider` + new `mitraChatRemainingSecondsProvider`)
  so WS `session_tick` frames don't invalidate the rest of the chat state

Dispose-in-ref bug fix:
- `home_screen.dart`, `payment_screen.dart`, `mitra_chat_screen.dart` —
  ref-using cleanup moved from `dispose()` to `deactivate()`. Modern
  Riverpod invalidates `ref` the moment `dispose()` runs; the resulting
  silent error corrupts the widget-tree finalize and the next screen
  appears frozen
- `halo_lints` package added at repo root with `no_ref_in_dispose` rule
  to catch this pattern in CI / IDE analysis
- `custom_lint` activated in both apps' `analysis_options.yaml`
  (was installed but never wired in — also brings `riverpod_lint`'s
  `avoid_ref_inside_state_dispose` online)
- CLAUDE.md Pitfalls section added to client_app + mitra_app

Phase 4 §3 retryable blast-failure (Option A):
- Backend `expirePairingRequest` + all-rejected use
  `recordIntermediateFailure` instead of `failPaymentSession` so the
  payment session stays `confirmed` for re-blast
- WS `pairing_failed` payload carries `is_terminal: false` on the
  retryable paths; client parses the flag and exposes `retryBlast()`
- "Coba cari lagi" CTA on S7 Timeout now re-blasts on the same payment
- Pairing service test updated to reflect the new semantics

Customer waiting-payment screen navigation patch:
- `_navigateTerminal` uses `Future.microtask` + `addPostFrameCallback`
  redundancy after a release-mode bug where polling stopped but
  `context.go` never fired, leaving the screen visually stuck on
  "menunggu pembayaran"

See requirement/resume-2026-05-15.md for next-day pickup checklist
(mitra release rebuild + S21 Ultra install + retest is the gating item).

Bundles unrelated in-flight Phase 4 §2.x work that was already on disk
(ESP screen removal, USP one-time gate scaffolding, bestie-availability
public route, OTP service edits, Maestro flow tweaks) — kept together
to avoid a partial-rebase mess.

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

client_app/lib/features/onboarding/screens/usp_screen.dart

@@ -1,13 +1,17 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 import '../../../core/theme/halo_tokens.dart';
 import '../../../core/theme/widgets/widgets.dart';
+import '../usp_seen_provider.dart';
 
-/// Onboarding step 2 — static value-prop ("USP") cards. No state; just a
-/// terminal CTA that routes onward to the auth/payment fork.
-class UspScreen extends StatelessWidget {
-  /// `verified` ➞ USP → OTP (`/auth/register`).
-  /// `anonymous` ➞ USP → `/payment/method-pick` (Stage 3 owns this route).
+/// Onboarding step 2 — static value-prop ("USP") cards. One-time gate
+/// (Phase 4, 2026-05-12): on Continue we mark the local `usp_seen` flag and
+/// best-effort persist to DB so this screen never shows again for this user.
+///
+/// `verified` ➞ USP → OTP (`/auth/register`).
+/// `anonymous` ➞ USP → `/payment/method-pick`.
+class UspScreen extends ConsumerWidget {
   final bool verified;
 
   const UspScreen({super.key, required this.verified});
@@ -36,7 +40,7 @@ class UspScreen extends StatelessWidget {
   ];
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context, WidgetRef ref) {
     return Scaffold(
       appBar: AppBar(
         title: const Padding(
@@ -90,7 +94,7 @@ class UspScreen extends StatelessWidget {
               HaloButton(
                 label: 'aku ngerti, lanjut',
                 fullWidth: true,
-                onPressed: () => _onContinue(context),
+                onPressed: () => _onContinue(context, ref),
               ),
             ],
           ),
@@ -99,12 +103,14 @@ class UspScreen extends StatelessWidget {
     );
   }
 
-  void _onContinue(BuildContext context) {
+  Future<void> _onContinue(BuildContext context, WidgetRef ref) async {
+    // Persist the local + server flag before leaving — next time the user
+    // hits VerifChoice, this screen is skipped.
+    await ref.read(uspSeenProvider.notifier).markSeen();
+    if (!context.mounted) return;
     if (verified) {
       context.push('/auth/register');
     } else {
-      // Stage 3 owns /payment/method-pick. Until then, route there as a
-      // placeholder; Maestro flow 03 stops at the route arrival.
       context.push('/payment/method-pick');
     }
   }