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/apps/openflare/proxy_route/build_helpers.go

@@ -90,7 +90,7 @@ func populateProxyRouteFields(
 	upstreams []string,
 	originHost, cachePolicy string,
 	limitConnPerServer, limitConnPerIP int,
-	limitRate, upstreamType string,
+	limitRate, limitReqPerIP, upstreamType string,
 ) {
 	route.SiteName = siteName
 	route.OriginID = originID
@@ -103,6 +103,7 @@ func populateProxyRouteFields(
 	route.LimitConnPerServer = limitConnPerServer
 	route.LimitConnPerIP = limitConnPerIP
 	route.LimitRate = limitRate
+	route.LimitReqPerIP = limitReqPerIP
 	route.CacheEnabled = input.CacheEnabled
 	route.CachePolicy = normalizeCachePolicy(input.CacheEnabled, cachePolicy)
 	route.CacheRules = jsonFields.cacheRulesJSON