feat(auth): transition from email to phone-based OTP authentication

- Replace Email+Password login with Phone+OTP flow
- Remove RegisterCubit and registration screens (email verification)
- Remove ResetPasswordCubit and reset password screens
- Add phone normalization and international dial code support
- Update LoginCubit with sendCode/resend cooldown logic
- Add new widgets: phone prefix selector, confirm sheet
- Update all auth API endpoints: /otp/send, /phone-session
- Update form inputs: Email -> Phone with E.164 validation
- Update tests for new auth flow

apps/lib/features/auth/data/auth_repository_impl.dart

@@ -19,30 +19,18 @@ class AuthRepositoryImpl implements AuthRepository {
        _onLogout = onLogout;
 
   @override
-  Future<VerificationCreateResponse> createVerification(
-    SignupStartRequest request,
-  ) {
-    return _api.createVerification(request);
+  Future<void> sendOtp(String phone) {
+    return _api.sendOtp(OtpSendRequest(phone: phone));
   }
 
   @override
-  Future<AuthResponse> verifyVerification(SignupVerifyRequest request) async {
-    final response = await _api.verifyVerification(request);
-    await _tokenStorage.saveTokens(
-      access: response.accessToken,
-      refresh: response.refreshToken,
+  Future<AuthResponse> createPhoneSession({
+    required String phone,
+    required String token,
+  }) async {
+    final response = await _api.createPhoneSession(
+      LoginRequest(phone: phone, token: token),
     );
-    return response;
-  }
-
-  @override
-  Future<void> resendVerification(SignupResendRequest request) {
-    return _api.resendVerification(request);
-  }
-
-  @override
-  Future<AuthResponse> createSession(LoginRequest request) async {
-    final response = await _api.createSession(request);
     await _tokenStorage.saveTokens(
       access: response.accessToken,
       refresh: response.refreshToken,
@@ -94,22 +82,4 @@ class AuthRepositoryImpl implements AuthRepository {
     final token = await _tokenStorage.getAccessToken();
     return token != null;
   }
-
-  @override
-  Future<void> requestPasswordReset(String email) {
-    return _api.requestPasswordReset(email);
-  }
-
-  @override
-  Future<void> confirmPasswordReset({
-    required String email,
-    required String token,
-    required String newPassword,
-  }) {
-    return _api.confirmPasswordReset(
-      email: email,
-      token: token,
-      newPassword: newPassword,
-    );
-  }
 }