feat(client/analytics): GA4 funnel instrumentation + unified home CTA

Add Firebase Analytics (GA4) funnel tracking to client_app:
- AnalyticsService typed wrapper (enum-gated, no PII) + analyticsProvider
- FirebaseAnalyticsObserver on GoRouter (screen_name via nameExtractor)
- user_id = customer UUID, user_type property, set on auth resolve/upgrade
- funnel events: curhat_start, curhat_repeat_start, auth_*, onboarding_usp_view,
  payment_view, payment_method_select, payment_started, pairing_matched/no_bestie
- bottom-sheet events: verif_choice_view/select, bestie_choice_view/select,
  extension_offer_view, chat_extension_requested
- payment_started carries app_instance_id + ga_session_id in the
  /payment-requests body for future server-side stitching (backend ignores)
- curhat_mode_pick screen name disambiguates the chat/call mode picker
  (/payment/method-pick) from the payment-channel picker (/payment/method)
- unify both home CTAs to "Aku Mau Curhat"

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

client_app/lib/core/analytics/analytics_service.dart

@@ -0,0 +1,254 @@
+import 'package:firebase_analytics/firebase_analytics.dart';
+import 'package:flutter/foundation.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+
+import '../../features/auth/widgets/verif_choice_sheet.dart' show VerifChoice;
+
+part 'analytics_service.g.dart';
+
+/// Which lifecycle funnel an event belongs to. GA4 reports filter on the
+/// `funnel` custom dimension; the activation and repeat funnels deliberately
+/// share event names and are split by this param (see
+/// requirement/analytics-funnel-plan.md §2/§5).
+enum AnalyticsFunnel {
+  activation('activation'),
+  repeat('repeat');
+
+  final String value;
+  const AnalyticsFunnel(this.value);
+}
+
+/// Identity method the user chose at the start of an auth flow. Low-cardinality
+/// and PII-free — the value is the *channel*, never the phone/email itself.
+enum AnalyticsAuthMethod {
+  phone('phone'),
+  google('google'),
+  apple('apple');
+
+  final String value;
+  const AnalyticsAuthMethod(this.value);
+}
+
+/// User-property bucket for `user_type`. Anonymous = server-issued anon
+/// customer with no identity; verified = phone/Google/Apple linked.
+enum AnalyticsUserType {
+  anonymous('anonymous'),
+  verified('verified');
+
+  final String value;
+  const AnalyticsUserType(this.value);
+}
+
+/// Stable screen names for the GoRouter observer. Keeping these as an enum
+/// (rather than mapping raw `state.uri.path`) guarantees path params like
+/// `:sessionId` / `:paymentId` / `:mitraId` never leak into `screen_name`.
+enum AnalyticsScreen {
+  splash('splash'),
+  authDisplayName('auth_display_name'),
+  authRegister('auth_register'),
+  authOtp('auth_otp'),
+  authSetName('auth_set_name'),
+  authForceRegister('auth_force_register'),
+  onboardingUspVerified('onboarding_usp_verified'),
+  onboardingUspAnon('onboarding_usp_anon'),
+  onboardingNotifGate('onboarding_notif_gate'),
+  home('home'),
+  profile('profile'),
+  paymentEntry('payment_entry'),
+  paymentDiscountPaywall('payment_discount_paywall'),
+  // Route /payment/method-pick is actually the chat-vs-call MODE picker
+  // ("pilih cara curhat"), NOT the payment-channel picker (that's
+  // paymentMethod → /payment/method). Named accordingly to avoid funnel
+  // ambiguity between the two.
+  curhatModePick('curhat_mode_pick'),
+  paymentDurationPick('payment_duration_pick'),
+  paymentMethod('payment_method'),
+  paymentWaiting('payment_waiting'),
+  paymentExpired('payment_expired'),
+  chatSearching('chat_searching'),
+  chatFound('chat_found'),
+  chatNoBestie('chat_no_bestie'),
+  chatWaitingTargeted('chat_waiting_targeted'),
+  chatSession('chat_session'),
+  chatThankYou('chat_thank_you'),
+  chatTabAktif('chat_tab_aktif'),
+  chatTabPembayaran('chat_tab_pembayaran'),
+  chatTabSelesai('chat_tab_selesai'),
+  chatTranscript('chat_transcript'),
+  bestieHistory('bestie_history');
+
+  final String value;
+  const AnalyticsScreen(this.value);
+}
+
+/// Thin, typed façade over `FirebaseAnalytics.instance`.
+///
+/// Every funnel event in requirement/analytics-funnel-plan.md §5 is a named
+/// method here so call sites never pass free-form strings — the only way to
+/// log is through a method whose params are fixed and PII-free. New events get
+/// added to the spec table first, then here (governance, §9).
+class AnalyticsService {
+  AnalyticsService(this._analytics);
+
+  final FirebaseAnalytics _analytics;
+
+  // ── Identity & user properties (§4) ───────────────────────────────────────
+
+  /// Set the opaque customer UUID. Re-set on identity upgrade (anon→verified)
+  /// so the same `user_id` continues across the merge. Never a phone/name.
+  Future<void> setUserId(String? customerId) =>
+      _analytics.setUserId(id: customerId);
+
+  Future<void> setUserType(AnalyticsUserType type) =>
+      _analytics.setUserProperty(name: 'user_type', value: type.value);
+
+  Future<void> setIsReturning(bool isReturning) => _analytics.setUserProperty(
+        name: 'is_returning',
+        value: isReturning ? 'true' : 'false',
+      );
+
+  // ── Payment stitching helpers (§3) ────────────────────────────────────────
+
+  /// App-instance id required by the GA4 Measurement Protocol to stitch a
+  /// server-fired `payment_confirmed` back to this device's stream.
+  Future<String?> appInstanceId() => _analytics.appInstanceId;
+
+  /// Current GA session id — replayed server-side so the MP event lands in the
+  /// same session as the client funnel.
+  Future<int?> sessionId() => _analytics.getSessionId();
+
+  // ── Funnel events (§5) ────────────────────────────────────────────────────
+
+  /// Activation: Home primary "aku mau curhat" CTA.
+  Future<void> logCurhatStart({String? entryPoint}) => _log('curhat_start', {
+        'funnel': AnalyticsFunnel.activation.value,
+        if (entryPoint != null) 'entry_point': entryPoint,
+      });
+
+  /// Repeat: returning "curhat sama bestie baru" / "curhat lagi" path.
+  Future<void> logCurhatRepeatStart() => _log('curhat_repeat_start', {
+        'funnel': AnalyticsFunnel.repeat.value,
+      });
+
+  /// Repeat: tapped a known bestie row in `/bestie/history`. `mitraRef` is an
+  /// opaque token (never the mitra's name/id surfaced to GA) — pass an
+  /// already-hashed/short ref or omit.
+  Future<void> logBestieReselect({String? mitraRef}) => _log('bestie_reselect', {
+        'funnel': AnalyticsFunnel.repeat.value,
+        if (mitraRef != null) 'mitra_ref': mitraRef,
+      });
+
+  Future<void> logAuthStart(AnalyticsAuthMethod method) => _log('auth_start', {
+        'method': method.value,
+      });
+
+  Future<void> logAuthOtpSubmit() => _log('auth_otp_submit', const {});
+
+  Future<void> logAuthComplete(AnalyticsUserType userType) =>
+      _log('auth_complete', {'user_type': userType.value});
+
+  Future<void> logOnboardingUspView({required bool verified}) =>
+      _log('onboarding_usp_view', {'verified': verified});
+
+  Future<void> logPaymentView({
+    required AnalyticsFunnel funnel,
+    required bool isRepeat,
+  }) =>
+      _log('payment_view', {
+        'funnel': funnel.value,
+        'is_repeat': isRepeat,
+      });
+
+  Future<void> logPaymentMethodSelect({required String method}) =>
+      _log('payment_method_select', {'method': method});
+
+  /// ⭐ Fired only AFTER the POST /payment-requests returns an id.
+  Future<void> logPaymentStarted({
+    required String paymentRequestId,
+    required int amount,
+    required String method,
+    required AnalyticsFunnel funnel,
+    required bool isRepeat,
+    required String productType,
+    required int durationMinutes,
+    String currency = 'IDR',
+  }) =>
+      _log('payment_started', {
+        'payment_request_id': paymentRequestId,
+        'amount': amount,
+        'currency': currency,
+        'method': method,
+        'funnel': funnel.value,
+        'is_repeat': isRepeat,
+        'product_type': productType,
+        'duration_minutes': durationMinutes,
+      });
+
+  Future<void> logPairingMatched({required AnalyticsFunnel funnel}) =>
+      _log('pairing_matched', {'funnel': funnel.value});
+
+  Future<void> logPairingNoBestie({required AnalyticsFunnel funnel}) =>
+      _log('pairing_no_bestie', {'funnel': funnel.value});
+
+  // ── Bottom-sheet / modal funnel events (§5) ───────────────────────────────
+
+  /// Activation: post-name Verif Choice Sheet shown. Paired with
+  /// [logVerifChoiceSelect] — the gap between view and select is abandonment.
+  Future<void> logVerifChoiceView() =>
+      _log('verif_choice_view', const {});
+
+  /// Activation: user picked an identity branch in the Verif Choice Sheet.
+  /// Maps the [VerifChoice] enum to a low-cardinality, PII-free channel value.
+  Future<void> logVerifChoiceSelect(VerifChoice choice) =>
+      _log('verif_choice_select', {
+        'choice': switch (choice) {
+          VerifChoice.verified => 'verified',
+          VerifChoice.anonymous => 'anonymous',
+        },
+      });
+
+  /// Repeat: Bestie Choice Sheet shown from the returning-user Home CTA.
+  Future<void> logBestieChoiceView() =>
+      _log('bestie_choice_view', const {});
+
+  /// Repeat: user picked a bestie branch in the Bestie Choice Sheet.
+  Future<void> logBestieChoiceSelect({required bool knownBestie}) =>
+      _log('bestie_choice_select', {
+        'choice': knownBestie ? 'known_bestie' : 'new_bestie',
+      });
+
+  /// Repeat: in-session extension upsell sheet shown (time-up / low-time).
+  Future<void> logExtensionOfferView({String? sessionId}) =>
+      _log('extension_offer_view', {
+        if (sessionId != null) 'session_id': sessionId,
+      });
+
+  /// Repeat: user confirmed an extension from the upsell sheet (not dismiss
+  /// or "akhiri sesi"). Fired the moment the perpanjang CTA is committed.
+  Future<void> logChatExtensionRequested({String? sessionId}) =>
+      _log('chat_extension_requested', {
+        if (sessionId != null) 'session_id': sessionId,
+      });
+
+  // ── Internal ──────────────────────────────────────────────────────────────
+
+  Future<void> _log(String name, Map<String, Object?> params) async {
+    final clean = <String, Object>{
+      for (final e in params.entries)
+        if (e.value != null) e.key: e.value!,
+    };
+    try {
+      await _analytics.logEvent(name: name, parameters: clean.isEmpty ? null : clean);
+    } catch (e) {
+      // Analytics must never break a user flow.
+      debugPrint('[analytics] failed to log $name: $e');
+    }
+  }
+}
+
+/// Keep-alive so a single AnalyticsService (and its FirebaseAnalytics handle)
+/// is shared across screens/notifiers for the app's lifetime.
+@Riverpod(keepAlive: true)
+AnalyticsService analytics(Ref ref) =>
+    AnalyticsService(FirebaseAnalytics.instance);

client_app/lib/core/analytics/analytics_service.g.dart

@@ -0,0 +1,29 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'analytics_service.dart';
+
+// **************************************************************************
+// RiverpodGenerator
+// **************************************************************************
+
+String _$analyticsHash() => r'862f59acd499543968f9ee591cec55cdd1b50035';
+
+/// Keep-alive so a single AnalyticsService (and its FirebaseAnalytics handle)
+/// is shared across screens/notifiers for the app's lifetime.
+///
+/// Copied from [analytics].
+@ProviderFor(analytics)
+final analyticsProvider = Provider<AnalyticsService>.internal(
+  analytics,
+  name: r'analyticsProvider',
+  debugGetCreateSourceHash:
+      const bool.fromEnvironment('dart.vm.product') ? null : _$analyticsHash,
+  dependencies: null,
+  allTransitiveDependencies: null,
+);
+
+@Deprecated('Will be removed in 3.0. Use Ref instead')
+// ignore: unused_element
+typedef AnalyticsRef = ProviderRef<AnalyticsService>;
+// ignore_for_file: type=lint
+// ignore_for_file: subtype_of_sealed_class, invalid_use_of_internal_member, invalid_use_of_visible_for_testing_member, deprecated_member_use_from_same_package

client_app/lib/core/auth/auth_notifier.g.dart

@@ -6,7 +6,7 @@ part of 'auth_notifier.dart';
 // RiverpodGenerator
 // **************************************************************************
 
-String _$authHash() => r'f0382b1380749cebe8182ad221023926768ebb92';
+String _$authHash() => r'76cd43babe5503d35a35c8fd23ba32afbc4c8c2d';
 
 /// See also [Auth].
 @ProviderFor(Auth)

client_app/lib/core/chat/chat_notifier.g.dart

@@ -30,7 +30,7 @@ final chatRemainingSecondsProvider = AutoDisposeStreamProvider<int>.internal(
 @Deprecated('Will be removed in 3.0. Use Ref instead')
 // ignore: unused_element
 typedef ChatRemainingSecondsRef = AutoDisposeStreamProviderRef<int>;
-String _$chatHash() => r'a42bf404f5b38034c6c9511259b64b1092af3caa';
+String _$chatHash() => r'56f019ce6e527128ab42a71f56220c5412cfec0f';
 
 /// See also [Chat].
 @ProviderFor(Chat)

client_app/lib/core/chat/session_closure_notifier.g.dart

@@ -6,7 +6,7 @@ part of 'session_closure_notifier.dart';
 // RiverpodGenerator
 // **************************************************************************
 
-String _$sessionClosureHash() => r'a9aaf26da64d3489497d057e2b05741c08444e07';
+String _$sessionClosureHash() => r'1ab9df044138115e232b3df494e2895177d9d66d';
 
 /// See also [SessionClosure].
 @ProviderFor(SessionClosure)

client_app/lib/core/pairing/pairing_notifier.g.dart

@@ -6,7 +6,7 @@ part of 'pairing_notifier.dart';
 // RiverpodGenerator
 // **************************************************************************
 
-String _$pairingHash() => r'd39980fe5b82348d03485006d0534ab597b93ceb';
+String _$pairingHash() => r'e66bbf67e1013b3d25230ed01fe2595bff943b3a';
 
 /// See also [Pairing].
 @ProviderFor(Pairing)