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/core/form_inputs/form_inputs.dart

@@ -13,16 +13,17 @@ class Username extends FormzInput<String, String> {
   }
 }
 
-class Email extends FormzInput<String, String> {
-  const Email.pure() : super.pure('');
-  const Email.dirty([super.value = '']) : super.dirty();
+class Phone extends FormzInput<String, String> {
+  const Phone.pure() : super.pure('');
+  const Phone.dirty([super.value = '']) : super.dirty();
 
-  static final _regex = RegExp(r'^[\w.-]+@[\w.-]+\.\w+$');
+  static final _regex = RegExp(r'^\d{7,14}$');
 
   @override
   String? validator(String value) {
-    if (value.isEmpty) return '请输入邮箱';
-    if (!_regex.hasMatch(value)) return '邮箱格式不正确';
+    final normalized = value.replaceAll(RegExp(r'\s+'), '');
+    if (normalized.isEmpty) return '请输入手机号';
+    if (!_regex.hasMatch(normalized)) return '手机号格式不正确';
     return null;
   }
 }