feat(relay): support configurable frps webui port and fix node detail integration

- Implement configurable FRPS WebUI switch and custom port setting (relay_frps_web_ui_port) in system configs.
- Integrate settings into Relay Node detail manage page instead of global settings.
- Dynamically query server version to select matching Docker image tag for Relay installation.
- Clean up legacy code and fix backend linter/test warnings.

internal/model/openflare_waf.go

@@ -313,7 +313,7 @@ func ListOpenFlareWAFRuleGroupBindingsByRouteID(ctx context.Context, routeID uin
 }
 
 func syncWAFBindingIDSequence(tx *gorm.DB) error {
-	if tx == nil || tx.Dialector.Name() != "postgres" {
+	if tx == nil || tx.Dialector.Name() != "postgres" { //nolint:staticcheck // QF1008: keep explicit Dialector field access
 		return nil
 	}
 	return tx.Exec(`

internal/model/system_configs.go

@@ -37,6 +37,8 @@ const (
 	ConfigKeyLoginSessionTTLHours             = "login_session_ttl_hours"             // 登录会话过期时间 (小时，0表示浏览器关闭后自动退出登录，-1表示永不过期)
 	ConfigKeyUpdateUpstreamRepository         = "update_upstream_repository"          // GitHub Actions Release 上游仓库
 	ConfigKeyStorageConfig                    = "storage_config"                      // 文件存储配置 (JSON)
+	ConfigKeyRelayFRPSWebUIEnabled            = "relay_frps_web_ui_enabled"            // 是否启用 FRPS 内置 Web 界面
+	ConfigKeyRelayFRPSWebUIPort               = "relay_frps_web_ui_port"               // FRPS 内置 Web 界面端口
 )
 
 const (