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/ui/widgets/password_field.dart

@@ -7,13 +7,13 @@ class PasswordField extends StatefulWidget {
   const PasswordField({
     super.key,
     required this.controller,
-    required this.label,
+    this.label,
     required this.hint,
     this.onChanged,
   });
 
   final TextEditingController controller;
-  final String label;
+  final String? label;
   final String hint;
   final ValueChanged<String>? onChanged;