feat(update): 添加在线更新和定价数据获取的代理支持

针对国内服务器访问 GitHub 困难的问题，为在线更新和定价数据获取功能添加代理支持。

主要变更：
- 新增 update.proxy_url 配置项，支持 http/https/socks5/socks5h 协议
- 修改 GitHubReleaseClient 和 PricingRemoteClient 支持代理配置
- 更新 Wire 依赖注入，通过 Provider 函数传递配置
- 更新 Docker 配置文件，支持通过 UPDATE_PROXY_URL 环境变量设置代理

配置示例：
  update:
    proxy_url: "http://127.0.0.1:7890"

Docker 环境变量：
  UPDATE_PROXY_URL=http://host.docker.internal:7890

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/cmd/server/wire_gen.go

@@ -114,7 +114,7 @@ func initializeApplication(buildInfo handler.BuildInfo) (*Application, error) {
 	adminRedeemHandler := admin.NewRedeemHandler(adminService)
 	settingHandler := admin.NewSettingHandler(settingService, emailService, turnstileService)
 	updateCache := repository.NewUpdateCache(redisClient)
-	gitHubReleaseClient := repository.NewGitHubReleaseClient()
+	gitHubReleaseClient := repository.ProvideGitHubReleaseClient(configConfig)
 	serviceBuildInfo := provideServiceBuildInfo(buildInfo)
 	updateService := service.ProvideUpdateService(updateCache, gitHubReleaseClient, serviceBuildInfo)
 	systemHandler := handler.ProvideSystemHandler(updateService)
@@ -125,7 +125,7 @@ func initializeApplication(buildInfo handler.BuildInfo) (*Application, error) {
 	userAttributeService := service.NewUserAttributeService(userAttributeDefinitionRepository, userAttributeValueRepository)
 	userAttributeHandler := admin.NewUserAttributeHandler(userAttributeService)
 	adminHandlers := handler.ProvideAdminHandlers(dashboardHandler, adminUserHandler, groupHandler, accountHandler, oAuthHandler, openAIOAuthHandler, geminiOAuthHandler, antigravityOAuthHandler, proxyHandler, adminRedeemHandler, settingHandler, systemHandler, adminSubscriptionHandler, adminUsageHandler, userAttributeHandler)
-	pricingRemoteClient := repository.NewPricingRemoteClient(configConfig)
+	pricingRemoteClient := repository.ProvidePricingRemoteClient(configConfig)
 	pricingService, err := service.ProvidePricingService(configConfig, pricingRemoteClient)
 	if err != nil {
 		return nil, err