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_api.dart

@@ -9,34 +9,13 @@ class AuthApi {
 
   AuthApi(this._client);
 
-  Future<VerificationCreateResponse> createVerification(
-    SignupStartRequest request,
-  ) async {
-    final response = await _client.post(
-      '$_prefix/verifications',
-      data: request.toJson(),
-    );
-    return VerificationCreateResponse.fromJson(response.data);
+  Future<void> sendOtp(OtpSendRequest request) async {
+    await _client.post('$_prefix/otp/send', data: request.toJson());
   }
 
-  Future<AuthResponse> verifyVerification(SignupVerifyRequest request) async {
+  Future<AuthResponse> createPhoneSession(LoginRequest request) async {
     final response = await _client.post(
-      '$_prefix/verify',
-      data: {'type': 'signup', ...request.toJson()},
-    );
-    return AuthResponse.fromJson(response.data);
-  }
-
-  Future<void> resendVerification(SignupResendRequest request) async {
-    await _client.post(
-      '$_prefix/resend',
-      data: {'type': 'signup', ...request.toJson()},
-    );
-  }
-
-  Future<AuthResponse> createSession(LoginRequest request) async {
-    final response = await _client.post(
-      '$_prefix/sessions',
+      '$_prefix/phone-session',
       data: request.toJson(),
     );
     return AuthResponse.fromJson(response.data);
@@ -53,27 +32,4 @@ class AuthApi {
   Future<void> deleteSession(LogoutRequest request) async {
     await _client.delete('$_prefix/sessions', data: request.toJson());
   }
-
-  Future<void> requestPasswordReset(String email) async {
-    await _client.post(
-      '$_prefix/resend',
-      data: {'type': 'recovery', 'email': email},
-    );
-  }
-
-  Future<void> confirmPasswordReset({
-    required String email,
-    required String token,
-    required String newPassword,
-  }) async {
-    await _client.post(
-      '$_prefix/verify',
-      data: {
-        'type': 'recovery',
-        'email': email,
-        'token': token,
-        'new_password': newPassword,
-      },
-    );
-  }
 }