feat: auto-restart server when listen addr or admin path changes

When admin config is updated with a new listen_addr or admin_path,
the server now automatically performs a graceful restart instead of
requiring the user to manually restart the service.

- cmd/main.go: refactor into a loop that supports graceful shutdown
  and restart via http.Server.Shutdown
- internal/admin/handlers.go: add SetOnRestart callback, triggered
  after config save when restart is required
- web/static/index.html: remove manual restart alert; auto-redirect
  to new admin path or show toast if port changed

via [HAPI](https://hapi.run)

Co-Authored-By: HAPI <[email protected]>

internal/admin/handlers.go

@@ -13,13 +13,18 @@ import (
 )
 
 type Handler struct {
-	cfg *config.Config
+	cfg         *config.Config
+	onRestart   func()
 }
 
 func NewHandler(cfg *config.Config) *Handler {
 	return &Handler{cfg: cfg}
 }
 
+func (h *Handler) SetOnRestart(fn func()) {
+	h.onRestart = fn
+}
+
 // GetLinks 获取所有链接
 func (h *Handler) GetLinks(w http.ResponseWriter, r *http.Request) {
 	links := h.cfg.ListLinks()
@@ -226,6 +231,10 @@ func (h *Handler) UpdateConfig(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if restartRequired && h.onRestart != nil {
+		go h.onRestart()
+	}
+
 	w.Header().Set("Content-Type", "application/json")
 	json.NewEncoder(w).Encode(map[string]interface{}{
 		"listen_addr":      h.cfg.ListenAddr,