Phase 4 Stage 2: onboarding redesign (client_app + mitra_app)

Verif Choice Sheet on display_name_screen drives the user into either
the verified or anonymous onboarding sub-flow. ESP screen (12 chips,
multi-select, info-only) + USP screen are shared between both branches;
selections persist through to chat_sessions.topics on session start.

OTP-blocked popup (HaloPopup) listens for the four real OTP-rate-limit
error codes (OTP_RATE_LIMIT_PHONE, OTP_RATE_LIMIT_IP, OTP_COOLDOWN,
OTP_ATTEMPTS_EXCEEDED) and drops the user onto the anonymous path with
ESP/USP state preserved.

Auth-providers gating replaces the --dart-define=ENABLE_SOCIAL_AUTH
build flag with server-driven discovery. authProvidersProvider preloads
GET /api/shared/auth-providers at cold start; welcome/register/
force-register screens render Google/Apple buttons only when the
backend reports enabled:true. Falls back to phone-OTP-only when both
providers are off. social_auth_enabled.dart deleted; client_app/CLAUDE.md
updated to reflect the new gating contract.

Mitra app: chat screen renders an ESP chip strip above the first message
bubble when chat_sessions.topics is non-empty.

Backend session.service.js getSessionById SELECTs cs.topics so the mitra
side can read the customer's selected topics.

Maestro flows 02_onboarding_verified.yaml + 03_onboarding_anon.yaml.

Deviation from plan: plan referenced OTP error code 'otp_retry_exhausted';
real codes are OTP_RATE_LIMIT_*/OTP_COOLDOWN/OTP_ATTEMPTS_EXCEEDED -
popup listens for all four. Plan said 'has_paid_first_session'; live
endpoint returns 'has_consulted_before' - used the live field.

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

client_app/lib/features/auth/widgets/otp_blocked_popup.dart

@@ -0,0 +1,57 @@
+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+import '../../../core/theme/halo_tokens.dart';
+import '../../../core/theme/widgets/widgets.dart';
+
+/// Modal shown when OTP delivery / verification is exhausted (rate-limited
+/// 429 from `OTP_RATE_LIMIT_PHONE`, `OTP_RATE_LIMIT_IP`, `OTP_COOLDOWN`, or
+/// `OTP_ATTEMPTS_EXCEEDED`). Offers a "lanjut tanpa verif" exit into the
+/// anonymous flow (preserving any ESP/USP state) and a stub "hubungi admin"
+/// affordance — Stage 8 will wire the real Tanya Admin sheet.
+class OtpBlockedPopup {
+  const OtpBlockedPopup._();
+
+  static Future<void> show(BuildContext context) {
+    return HaloPopup.show<void>(
+      context,
+      title: 'Verifikasi nomor lagi penuh',
+      body:
+          'Sistem lagi nahan permintaan OTP buat keamanan. Kamu bisa lanjut '
+          'tanpa verifikasi, atau hubungi admin biar dibantu manual.',
+      icon: Container(
+        width: 64,
+        height: 64,
+        decoration: const BoxDecoration(
+          color: HaloTokens.brandSofter,
+          shape: BoxShape.circle,
+        ),
+        alignment: Alignment.center,
+        child: const Icon(
+          Icons.lock_clock_outlined,
+          color: HaloTokens.brandDark,
+          size: 28,
+        ),
+      ),
+      primary: HaloPopupAction(
+        label: 'lanjut tanpa verif',
+        onPressed: () {
+          // ESP/USP picks live in Riverpod providers (espSelectionProvider,
+          // espSkippedProvider) and survive this navigation — no need to pass
+          // them as `extra`.
+          context.go('/onboarding/anon/method');
+        },
+      ),
+      secondary: HaloPopupAction(
+        label: 'hubungi admin',
+        onPressed: () {
+          // TODO(stage8): replace with Tanya Admin sheet.
+          ScaffoldMessenger.of(context).showSnackBar(
+            const SnackBar(
+              content: Text('Tanya Admin akan tersedia segera.'),
+            ),
+          );
+        },
+      ),
+    );
+  }
+}