feat: implement custom WebUI support with dynamic frontend replacement

- Add WebUI service and controller for managing custom frontend packages

- Allow overriding default static assets when custom WebUI is activated

- Add Make commands for packing custom WebUI distributions

- Update UI settings to support uploading, activating and deleting WebUIs

- Document WebUI feature in README and changelog

internal/router/api_routes.go

@@ -64,6 +64,7 @@ func initAuthorizedAPIRoutes(api *gin.RouterGroup, c *Controllers) {
 			registerNotificationRoutes(adminOnly, c)
 			registerAppLogRoutes(adminOnly, c)
 			registerSystemWSRoutes(adminOnly, c)
+			registerWebUIRoutes(adminOnly, c)
 		}
 	}
 
@@ -276,3 +277,13 @@ func initAgentAPIRoutes(root *gin.RouterGroup, c *Controllers) {
 		agentAPI.GET("/ws", c.Agent.WSConnect)      // WebSocket 连接
 	}
 }
+
+func registerWebUIRoutes(g *gin.RouterGroup, c *Controllers) {
+	webuiGroup := g.Group("/webui")
+	{
+		webuiGroup.GET("", c.WebUI.GetWebUIs)
+		webuiGroup.POST("/upload", c.WebUI.UploadWebUI)
+		webuiGroup.PUT("/active", c.WebUI.SetActiveWebUI)
+		webuiGroup.DELETE("/:name", c.WebUI.DeleteWebUI)
+	}
+}