feat(rate-limit): add default request rate limit configuration

- Support openresty_default_limit_req_per_ip in system_configs.
- Add limit_req and limit_req_status 429 directive generation in openresty renderer.
- Implement route-level limit_req_per_ip override and explicit disable.
- Add frontend UI inputs and validation in rate limits tab config.
- Update swagger API docs and changelog for v3.4.3-beta.3.

internal/model/openflare_proxy_route.go

@@ -25,6 +25,7 @@ type ProxyRoute struct {
 	LimitConnPerServer   int          `json:"limit_conn_per_server" gorm:"not null;default:0"`
 	LimitConnPerIP       int          `json:"limit_conn_per_ip" gorm:"not null;default:0"`
 	LimitRate            string       `json:"limit_rate" gorm:"size:32;not null;default:''"`
+	LimitReqPerIP        string       `json:"limit_req_per_ip" gorm:"size:32;not null;default:''"`
 	CacheEnabled         bool         `json:"cache_enabled" gorm:"not null;default:false"`
 	CachePolicy          string       `json:"cache_policy" gorm:"size:32;not null;default:''"`
 	CacheRules           string       `json:"cache_rules" gorm:"type:text;not null;default:'[]'"`
@@ -84,6 +85,7 @@ func UpdateProxyRouteRecord(ctx context.Context, route *ProxyRoute) error {
 		"limit_conn_per_server":  route.LimitConnPerServer,
 		"limit_conn_per_ip":      route.LimitConnPerIP,
 		"limit_rate":             route.LimitRate,
+		"limit_req_per_ip":       route.LimitReqPerIP,
 		"cache_enabled":          route.CacheEnabled,
 		"cache_policy":           route.CachePolicy,
 		"cache_rules":            route.CacheRules,

internal/model/system_configs.go

@@ -108,6 +108,7 @@ const (
 	ConfigKeyOpenRestyDefaultLimitConnPerServer    = "openresty_default_limit_conn_per_server"   // 默认站点并发连接
 	ConfigKeyOpenRestyDefaultLimitConnPerIP        = "openresty_default_limit_conn_per_ip"       // 默认单 IP 并发连接
 	ConfigKeyOpenRestyDefaultLimitRate             = "openresty_default_limit_rate"              // 默认单请求带宽
+	ConfigKeyOpenRestyDefaultLimitReqPerIP         = "openresty_default_limit_req_per_ip"        // 默认单 IP 请求频率限制
 )
 
 const (