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/verif_choice_sheet.dart

@@ -0,0 +1,77 @@
+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+import '../../../core/theme/halo_tokens.dart';
+import '../../../core/theme/widgets/widgets.dart';
+
+/// Result of the post-name Verif Choice Sheet. Caller routes to the matching
+/// onboarding sub-flow.
+enum VerifChoice { verified, anonymous }
+
+class VerifChoiceSheet extends StatelessWidget {
+  const VerifChoiceSheet({super.key});
+
+  /// Show the sheet and return the user's choice (`null` if dismissed).
+  static Future<VerifChoice?> show(BuildContext context) {
+    return HaloBottomSheet.show<VerifChoice>(
+      context,
+      child: const VerifChoiceSheet(),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      mainAxisSize: MainAxisSize.min,
+      crossAxisAlignment: CrossAxisAlignment.stretch,
+      children: [
+        const Text(
+          'Mau curhat sebagai siapa?',
+          style: TextStyle(
+            fontFamily: HaloTokens.fontDisplay,
+            fontSize: 22,
+            height: 28 / 22,
+            fontWeight: FontWeight.w700,
+            color: HaloTokens.ink,
+          ),
+        ),
+        const SizedBox(height: HaloSpacing.s8),
+        const Text(
+          'Verifikasi nomor HP biar bisa dapet diskon sesi pertama dan riwayat curhatmu kesimpan. Atau langsung curhat anonim, nggak perlu daftar.',
+          style: TextStyle(
+            fontFamily: HaloTokens.fontBody,
+            fontSize: 14,
+            height: 20 / 14,
+            color: HaloTokens.inkSoft,
+          ),
+        ),
+        const SizedBox(height: HaloSpacing.s24),
+        HaloButton(
+          label: 'verifikasi nomor HP',
+          fullWidth: true,
+          onPressed: () =>
+              Navigator.of(context).pop(VerifChoice.verified),
+        ),
+        const SizedBox(height: HaloSpacing.s12),
+        HaloButton(
+          label: 'curhat anonim',
+          variant: HaloButtonVariant.secondary,
+          fullWidth: true,
+          onPressed: () =>
+              Navigator.of(context).pop(VerifChoice.anonymous),
+        ),
+      ],
+    );
+  }
+}
+
+/// Helper: route to the right onboarding sub-flow for a verif choice.
+void routeForVerifChoice(BuildContext context, VerifChoice choice) {
+  switch (choice) {
+    case VerifChoice.verified:
+      context.push('/onboarding/verif/esp');
+      break;
+    case VerifChoice.anonymous:
+      context.push('/onboarding/anon/esp');
+      break;
+  }
+}