Merge PR #73: feat(antigravity): 添加 Antigravity (Cloud AI Companion) 平台支持

新增功能:
- Antigravity OAuth 授权流程支持
- Claude → Gemini 协议转换（Claude API 请求自动转换为 Gemini 格式）
- 配额刷新和状态显示
- 混合调度功能，支持 Anthropic 和 Antigravity 账户混合使用
- /antigravity 专用路由，支持仅使用 Antigravity 账户
- 前端 Antigravity 服务商标识和账户管理功能

冲突解决:
- CreateAccountModal.vue: 合并 data-tour 属性和 mixed-scheduling 属性
- EditAccountModal.vue: 合并 data-tour 属性和 mixed-scheduling 属性

代码质量改进:
- 修复 antigravity 类型文件的 gofmt 格式问题（struct 字段对齐、interface{} → any）
- 移除 .golangci.yml 中的 gofmt 排除规则
- 修复测试文件的格式问题

backend/internal/service/token_refresh_service.go

@@ -27,6 +27,7 @@ func NewTokenRefreshService(
 	oauthService *OAuthService,
 	openaiOAuthService *OpenAIOAuthService,
 	geminiOAuthService *GeminiOAuthService,
+	antigravityOAuthService *AntigravityOAuthService,
 	cfg *config.Config,
 ) *TokenRefreshService {
 	s := &TokenRefreshService{
@@ -40,6 +41,7 @@ func NewTokenRefreshService(
 		NewClaudeTokenRefresher(oauthService),
 		NewOpenAITokenRefresher(openaiOAuthService),
 		NewGeminiTokenRefresher(geminiOAuthService),
+		NewAntigravityTokenRefresher(antigravityOAuthService),
 	}
 
 	return s

backend/internal/web/embed_on.go

@@ -28,6 +28,7 @@ func ServeEmbeddedFrontend() gin.HandlerFunc {
 		if strings.HasPrefix(path, "/api/") ||
 			strings.HasPrefix(path, "/v1/") ||
 			strings.HasPrefix(path, "/v1beta/") ||
+			strings.HasPrefix(path, "/antigravity/") ||
 			strings.HasPrefix(path, "/setup/") ||
 			path == "/health" ||
 			path == "/responses" {

frontend/src/api/admin/index.ts

@@ -14,6 +14,7 @@ import systemAPI from './system'
 import subscriptionsAPI from './subscriptions'
 import usageAPI from './usage'
 import geminiAPI from './gemini'
+import antigravityAPI from './antigravity'
 
 /**
  * Unified admin API object for convenient access
@@ -29,7 +30,8 @@ export const adminAPI = {
   system: systemAPI,
   subscriptions: subscriptionsAPI,
   usage: usageAPI,
-  gemini: geminiAPI
+  gemini: geminiAPI,
+  antigravity: antigravityAPI
 }
 
 export {
@@ -43,7 +45,8 @@ export {
   systemAPI,
   subscriptionsAPI,
   usageAPI,
-  geminiAPI
+  geminiAPI,
+  antigravityAPI
 }
 
 export default adminAPI

frontend/src/components/common/PlatformIcon.vue

@@ -15,6 +15,10 @@
   <svg v-else-if="platform === 'gemini'" :class="sizeClass" viewBox="0 0 24 24" fill="currentColor">
     <path d="M12 2l1.89 7.2L21 12l-7.11 2.8L12 22l-1.89-7.2L3 12l7.11-2.8L12 2z" />
   </svg>
+  <!-- Antigravity logo (cloud) -->
+  <svg v-else-if="platform === 'antigravity'" :class="sizeClass" viewBox="0 0 24 24" fill="currentColor">
+    <path d="M19.35 10.04C18.67 6.59 15.64 4 12 4 9.11 4 6.6 5.64 5.35 8.04 2.34 8.36 0 10.91 0 14c0 3.31 2.69 6 6 6h13c2.76 0 5-2.24 5-5 0-2.64-2.05-4.78-4.65-4.96z" />
+  </svg>
   <!-- Fallback: generic platform icon -->
   <svg v-else :class="sizeClass" fill="currentColor" viewBox="0 0 24 24">
     <path