feat: SMS OTP phone auth + mandatory phone verification gate

- MyUser: add isPhoneVerified field (from is_phone_verified in API)
- ApiUserRepository: signInWithPhoneNumber calls POST /auth/send-otp,
  verifyOTP calls POST /auth/phone, linkWithOTP calls POST /auth/verify-phone
  Added updateFcmToken and changePassword methods
- AuthBloc: remove Firebase PhoneVerificationService, use repository OTP flow
- app_view.dart: gate authenticated users without verified phone to
  PhoneVerifyRequiredScreen before showing HomeScreen
- welcome_screen.dart: full redesign with gradient header, logo, integrated
  OTP flow (phone → code in same screen), 60s resend timer
- PhoneVerifyRequiredScreen: new screen for users who need to verify phone

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/user_repository/lib/src/models/my_user.dart

@@ -13,6 +13,7 @@ class MyUser extends Equatable {
   final String? gender;
   final ProState proState;
   final String? token;
+  final bool isPhoneVerified;
 
   const MyUser({
     required this.id,
@@ -26,6 +27,7 @@ class MyUser extends Equatable {
     this.gender,
     required this.proState,
     this.token,
+    this.isPhoneVerified = false,
   });
 
   get drawerLabel => email != null && email!.isNotEmpty
@@ -47,6 +49,7 @@ class MyUser extends Equatable {
     gender: '',
     proState: ProState.inactive,
     token: '',
+    isPhoneVerified: false,
   );
 
   /// Modify MyUser parameters
@@ -62,6 +65,7 @@ class MyUser extends Equatable {
     String? gender,
     ProState? proState,
     String? token,
+    bool? isPhoneVerified,
   }) {
     return MyUser(
       id: id ?? this.id,
@@ -75,6 +79,7 @@ class MyUser extends Equatable {
       gender: gender ?? this.gender,
       proState: proState ?? this.proState,
       token: token ?? this.token,
+      isPhoneVerified: isPhoneVerified ?? this.isPhoneVerified,
     );
   }
 
@@ -129,5 +134,6 @@ class MyUser extends Equatable {
         gender,
         proState,
         token,
+        isPhoneVerified,
       ];
 }