perf(认证): 引入 API Key 认证缓存与轻量删除查询

增加 L1/L2 缓存、负缓存与单飞回源
使用 key+owner 轻量查询替代全量加载并清理旧接口
补充缓存失效与余额更新测试，修复随机抖动 lint

测试: make test

backend/internal/service/wire.go

@@ -77,12 +77,18 @@ func ProvideConcurrencyService(cache ConcurrencyCache, accountRepo AccountReposi
 	return svc
 }
 
+// ProvideAPIKeyAuthCacheInvalidator 提供 API Key 认证缓存失效能力
+func ProvideAPIKeyAuthCacheInvalidator(apiKeyService *APIKeyService) APIKeyAuthCacheInvalidator {
+	return apiKeyService
+}
+
 // ProviderSet is the Wire provider set for all services
 var ProviderSet = wire.NewSet(
 	// Core services
 	NewAuthService,
 	NewUserService,
 	NewAPIKeyService,
+	ProvideAPIKeyAuthCacheInvalidator,
 	NewGroupService,
 	NewAccountService,
 	NewProxyService,