fix: correct static file routing for dashboard assets

Mapped /css, /js, and /img to their respective subdirectories in ./static to resolve 404 errors.

internal/server/server.go

@@ -77,9 +77,11 @@ func (s *Server) setupRoutes() {
 	s.router.Use(middleware.AuthMiddleware(s.database))
 
 	// Static files
-	s.router.Static("/static", "./static")
 	s.router.StaticFile("/", "./static/index.html")
 	s.router.StaticFile("/favicon.ico", "./static/favicon.ico")
+	s.router.Static("/css", "./static/css")
+	s.router.Static("/js", "./static/js")
+	s.router.Static("/img", "./static/img")
 
 	// WebSocket
 	s.router.GET("/ws", s.handleWebSocket)