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/auth/widgets/verif_choice_sheet.dart

@@ -1,7 +1,9 @@
 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 '../../onboarding/usp_seen_provider.dart';
 
 /// Result of the post-name Verif Choice Sheet. Caller routes to the matching
 /// onboarding sub-flow.
@@ -65,13 +67,26 @@ class VerifChoiceSheet extends StatelessWidget {
 }
 
 /// Helper: route to the right onboarding sub-flow for a verif choice.
-void routeForVerifChoice(BuildContext context, VerifChoice choice) {
+///
+/// Phase 4 (2026-05-12): the S5 ESP screen is retired and S5b USP is now a
+/// one-time gate. If the user has already seen USP (local SharedPreferences
+/// flag, OR-merged with `customers.usp_seen` on login), we skip USP entirely
+/// and jump to the per-branch next step.
+Future<void> routeForVerifChoice(
+  BuildContext context,
+  WidgetRef ref,
+  VerifChoice choice,
+) async {
+  final seen = await ref.read(uspSeenProvider.future);
+  if (!context.mounted) return;
   switch (choice) {
     case VerifChoice.verified:
-      context.push('/onboarding/verif/esp');
+      context.push(seen ? '/auth/register' : '/onboarding/verif/usp');
       break;
     case VerifChoice.anonymous:
-      context.push('/onboarding/anon/esp');
+      // `/onboarding/anon/method` redirects to `/payment/method-pick`; use the
+      // canonical destination here.
+      context.push(seen ? '/payment/method-pick' : '/onboarding/anon/usp');
       break;
   }
 }