feat(ops): 添加运维监控配置开关

- 在 .env.example 和 config.example.yaml 中添加 ops.enabled 配置项
- 默认值为 true，保持现有行为
- 当设置为 false 时，左侧栏隐藏运维监控菜单并禁用所有运维监控功能
- 修改后端 GetSettings API，让 ops_monitoring_enabled 受 config.ops.enabled 控制
- 数据清理和预聚合任务默认保持开启状态（通过运维监控设置对话框配置）

backend/cmd/server/wire_gen.go

@@ -115,7 +115,6 @@ func initializeApplication(buildInfo handler.BuildInfo) (*Application, error) {
 	proxyHandler := admin.NewProxyHandler(adminService)
 	adminRedeemHandler := admin.NewRedeemHandler(adminService)
 	promoHandler := admin.NewPromoHandler(promoService)
-	settingHandler := admin.NewSettingHandler(settingService, emailService, turnstileService)
 	opsRepository := repository.NewOpsRepository(db)
 	pricingRemoteClient := repository.ProvidePricingRemoteClient(configConfig)
 	pricingService, err := service.ProvidePricingService(configConfig, pricingRemoteClient)
@@ -131,6 +130,7 @@ func initializeApplication(buildInfo handler.BuildInfo) (*Application, error) {
 	openAIGatewayService := service.NewOpenAIGatewayService(accountRepository, usageLogRepository, userRepository, userSubscriptionRepository, gatewayCache, configConfig, concurrencyService, billingService, rateLimitService, billingCacheService, httpUpstream, deferredService)
 	geminiMessagesCompatService := service.NewGeminiMessagesCompatService(accountRepository, groupRepository, gatewayCache, geminiTokenProvider, rateLimitService, httpUpstream, antigravityGatewayService, configConfig)
 	opsService := service.NewOpsService(opsRepository, settingRepository, configConfig, accountRepository, concurrencyService, gatewayService, openAIGatewayService, geminiMessagesCompatService, antigravityGatewayService)
+	settingHandler := admin.NewSettingHandler(settingService, emailService, turnstileService, opsService)
 	opsHandler := admin.NewOpsHandler(opsService)
 	updateCache := repository.NewUpdateCache(redisClient)
 	gitHubReleaseClient := repository.ProvideGitHubReleaseClient(configConfig)