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/shared/utils/validators.dart

@@ -1,13 +1,13 @@
 class Validators {
   Validators._();
 
-  static String? email(String? value) {
+  static String? phone(String? value) {
     if (value == null || value.isEmpty) {
-      return '请输入邮箱';
+      return '请输入手机号';
     }
-    final emailRegex = RegExp(r'^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$');
-    if (!emailRegex.hasMatch(value)) {
-      return '请输入有效的邮箱地址';
+    final phoneRegex = RegExp(r'^\+861[3-9]\d{9}$');
+    if (!phoneRegex.hasMatch(value)) {
+      return '请输入有效的 +86 手机号';
     }
     return null;
   }