Make healthz endpoint verify upload directory is accessible

main.go

@@ -107,6 +107,7 @@ func handleRequest(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	if r.Method == "GET" && r.URL.Path == "/healthz" {
+		handleHealthz(w, r)
 		return
 	}
 
@@ -133,6 +134,15 @@ func handleRequest(w http.ResponseWriter, r *http.Request) {
 	logRequest(r, 405, time.Since(start))
 }
 
+func handleHealthz(w http.ResponseWriter, r *http.Request) {
+	if _, err := os.Stat(uploadDir); err != nil {
+		log.Printf("Healthz check failed: %v", err)
+		http.Error(w, "Upload directory is not accessible", http.StatusServiceUnavailable)
+		return
+	}
+	w.WriteHeader(http.StatusOK)
+}
+
 func handleUpload(w http.ResponseWriter, r *http.Request, start time.Time) {
 	filename := strings.TrimPrefix(r.URL.Path, "/")
 	if filename == "" {