fun: add BindRoute for custom HTTP routes (GET/POST, form-data callbacks)

- BindRoute(method, path, handler) with exact-match routing dispatched before /cell RPC
- RouteCtx merges query args and form-urlencoded POST args for callback scenarios (e.g. epay notify)
- handler returns error -> unified Result error response; nil -> full control via fasthttp.RequestCtx (plain-text 'success' replies)
- /cell reserved; duplicate/invalid registration panics at startup; all existing tests pass

handle.go

@@ -11,11 +11,16 @@ import (
 	"github.com/valyala/fasthttp"
 )
 
-// handle 处理 HTTP 请求
+// handle 处理 HTTP 请求：先匹配自定义路由（BindRoute），未命中走 /cell RPC
 func (f *Fun) handle(fastCtx *fasthttp.RequestCtx) {
 	ctx := &Ctx{RequestCtx: fastCtx}
 	defer f.handlePanic(ctx)
 
+	if handler, ok := f.routes[string(fastCtx.Method())+" "+string(fastCtx.Path())]; ok {
+		f.handleRoute(fastCtx, handler)
+		return
+	}
+
 	if ctx.path() != "/cell" {
 		ctx.setStatusCode(fasthttp.StatusNotFound)
 		return