feat(auth): 接入 Google 登录

- 登录页保留邮箱与 Google 两个入口，Google 按钮按官方规范改为白底四色图标
- 新增 GoogleAuthService：封装 initialize/authenticate，失败以结果对象返回
- AuthApi 增加 googleLogin，AuthController 增加 signInWithGoogle
- iOS 补充 CFBundleURLTypes 与 GIDClientID，Bundle ID 统一为 com.stormg.lumadrama
- Google 请求期间按钮显示转圈并禁止重复点击

test/auth/auth_visual_test.dart

@@ -90,28 +90,17 @@ void main() {
         tester.getSize(find.byKey(const Key('auth-brand-logo'))),
         const Size(88, 88),
       );
-      expect(find.byKey(const Key('auth-entry-google')), findsNothing);
-      expect(find.byKey(const Key('auth-entry-phone')), findsOneWidget);
+      expect(find.byKey(const Key('auth-entry-google')), findsOneWidget);
+      expect(find.byKey(const Key('auth-entry-phone')), findsNothing);
       expect(find.byKey(const Key('auth-entry-email')), findsOneWidget);
       expect(find.byKey(const Key('auth-legal')), findsOneWidget);
-      expect(
-        tester.getSize(find.byKey(const Key('auth-entry-phone'))).height,
-        52,
-      );
       expect(
         tester.getSize(find.byKey(const Key('auth-entry-email'))).height,
         52,
       );
-      final phoneButton = tester.widget<Material>(
-        find.descendant(
-          of: find.byKey(const Key('auth-entry-phone')),
-          matching: find.byType(Material),
-        ),
-      );
-      expect(phoneButton.color, AppColors.brandRed);
       expect(
-        (phoneButton.shape! as RoundedRectangleBorder).borderRadius,
-        BorderRadius.circular(26),
+        tester.getSize(find.byKey(const Key('auth-entry-google'))).height,
+        52,
       );
       final emailButton = tester.widget<Material>(
         find.descendant(
@@ -119,8 +108,20 @@ void main() {
           matching: find.byType(Material),
         ),
       );
-      // 次按钮是「白 6%」玻璃拟态，不再有描边。
-      expect(emailButton.color, Colors.white.withValues(alpha: 0.06));
+      // 邮箱是主入口，用品牌红。
+      expect(emailButton.color, AppColors.brandRed);
+      expect(
+        (emailButton.shape! as RoundedRectangleBorder).borderRadius,
+        BorderRadius.circular(26),
+      );
+      final googleButton = tester.widget<Material>(
+        find.descendant(
+          of: find.byKey(const Key('auth-entry-google')),
+          matching: find.byType(Material),
+        ),
+      );
+      // 第三方登录按 Google 规范用白底深字。
+      expect(googleButton.color, Colors.white);
 
       final glow = tester.widget<DecoratedBox>(
         find.byKey(const Key('auth-red-glow')),
@@ -237,7 +238,7 @@ void main() {
     expect(tester.getCenter(logo).dx, closeTo(195, 0.1));
     expect(
       tester.getBottomLeft(logo).dy,
-      lessThan(tester.getTopLeft(find.byKey(const Key('auth-entry-phone'))).dy),
+      lessThan(tester.getTopLeft(find.byKey(const Key('auth-entry-email'))).dy),
     );
   });