Fix onboarding UX and add replaceable journey analytics

Make recipient changes explicit, prioritize verification retry, and label simulated outcomes prominently. Add shared typed analytics with bounded dummy capture, correlated service events and documented PostHog adapter contract. Validate privacy, retries, abandonment, keyboard recovery and accessibility. Related to #12.

frontend/app/lib/generated/i18n/app_localizations.dart

@@ -461,7 +461,7 @@ abstract class AppLocalizations {
   /// No description provided for @verificationRetry.
   ///
   /// In en, this message translates to:
-  /// **'Try again'**
+  /// **'Retry verification'**
   String get verificationRetry;
 
   /// No description provided for @verificationBack.
@@ -493,6 +493,48 @@ abstract class AppLocalizations {
   /// In en, this message translates to:
   /// **'CONFIRM YOUR EMAIL'**
   String get verificationStep;
+
+  /// No description provided for @demoSentHeading.
+  ///
+  /// In en, this message translates to:
+  /// **'Demo email prepared.'**
+  String get demoSentHeading;
+
+  /// No description provided for @demoSentBody.
+  ///
+  /// In en, this message translates to:
+  /// **'No email was sent. Use the demo confirmation below to preview the next step.'**
+  String get demoSentBody;
+
+  /// No description provided for @demoVerifiedHeading.
+  ///
+  /// In en, this message translates to:
+  /// **'Demo verification\ncomplete.'**
+  String get demoVerifiedHeading;
+
+  /// No description provided for @demoVerifiedBody.
+  ///
+  /// In en, this message translates to:
+  /// **'You’ve previewed email confirmation. No account was verified. Return to login to explore the demo.'**
+  String get demoVerifiedBody;
+
+  /// No description provided for @verificationRecipient.
+  ///
+  /// In en, this message translates to:
+  /// **'Recipient'**
+  String get verificationRecipient;
+
+  /// No description provided for @verificationChangeEmail.
+  ///
+  /// In en, this message translates to:
+  /// **'Change email'**
+  String get verificationChangeEmail;
+
+  /// No description provided for @demoResend.
+  ///
+  /// In en, this message translates to:
+  /// **'Prepare demo email again'**
+  String get demoResend;
 }
 
 class _AppLocalizationsDelegate

frontend/app/lib/generated/i18n/app_localizations_en.dart

@@ -201,7 +201,7 @@ class AppLocalizationsEn extends AppLocalizations {
   String get verificationRequest => 'Send a new verification email';
 
   @override
-  String get verificationRetry => 'Try again';
+  String get verificationRetry => 'Retry verification';
 
   @override
   String get verificationBack => 'Back to login';
@@ -219,4 +219,27 @@ class AppLocalizationsEn extends AppLocalizations {
 
   @override
   String get verificationStep => 'CONFIRM YOUR EMAIL';
+
+  @override
+  String get demoSentHeading => 'Demo email prepared.';
+
+  @override
+  String get demoSentBody =>
+      'No email was sent. Use the demo confirmation below to preview the next step.';
+
+  @override
+  String get demoVerifiedHeading => 'Demo verification\ncomplete.';
+
+  @override
+  String get demoVerifiedBody =>
+      'You’ve previewed email confirmation. No account was verified. Return to login to explore the demo.';
+
+  @override
+  String get verificationRecipient => 'Recipient';
+
+  @override
+  String get verificationChangeEmail => 'Change email';
+
+  @override
+  String get demoResend => 'Prepare demo email again';
 }

frontend/app/lib/generated/i18n/app_localizations_ru.dart

@@ -202,7 +202,7 @@ class AppLocalizationsRu extends AppLocalizations {
   String get verificationRequest => 'Отправить новое письмо';
 
   @override
-  String get verificationRetry => 'Попробовать ещё раз';
+  String get verificationRetry => 'Повторить подтверждение';
 
   @override
   String get verificationBack => 'Вернуться ко входу';
@@ -220,4 +220,27 @@ class AppLocalizationsRu extends AppLocalizations {
 
   @override
   String get verificationStep => 'ПОДТВЕРДИТЕ ПОЧТУ';
+
+  @override
+  String get demoSentHeading => 'Демописьмо готово.';
+
+  @override
+  String get demoSentBody =>
+      'Письмо не отправлено. Используйте демоссылку ниже, чтобы посмотреть следующий шаг.';
+
+  @override
+  String get demoVerifiedHeading => 'Демоподтверждение\nзавершено.';
+
+  @override
+  String get demoVerifiedBody =>
+      'Вы посмотрели подтверждение почты. Реальный аккаунт не подтверждён. Вернитесь ко входу, чтобы продолжить знакомство с демоверсией.';
+
+  @override
+  String get verificationRecipient => 'Получатель';
+
+  @override
+  String get verificationChangeEmail => 'Изменить почту';
+
+  @override
+  String get demoResend => 'Подготовить демописьмо ещё раз';
 }