Build request data through RequestData struct instead of fasthttp directly

Refactor request generators to populate a script.RequestData intermediate struct, then apply it to fasthttp.Request in one step. This eliminates the round-trip conversion (fasthttp → RequestData → fasthttp) when scripts are enabled. Remove the URL field from RequestData and the now-unused fasthttp conversion functions from chain.go.

internal/script/lua.go

@@ -90,7 +90,6 @@ func (e *LuaEngine) requestDataToTable(req *RequestData) *lua.LTable {
 	t := L.NewTable()
 
 	t.RawSetString("method", lua.LString(req.Method))
-	t.RawSetString("url", lua.LString(req.URL))
 	t.RawSetString("path", lua.LString(req.Path))
 	t.RawSetString("body", lua.LString(req.Body))
 
@@ -137,11 +136,6 @@ func (e *LuaEngine) tableToRequestData(t *lua.LTable, req *RequestData) {
 		req.Method = string(v.(lua.LString))
 	}
 
-	// URL
-	if v := t.RawGetString("url"); v.Type() == lua.LTString {
-		req.URL = string(v.(lua.LString))
-	}
-
 	// Path
 	if v := t.RawGetString("path"); v.Type() == lua.LTString {
 		req.Path = string(v.(lua.LString))