Fix mail queue and logs commands

- Hardcode paths: /usr/sbin/postqueue, /usr/sbin/postsuper, /usr/bin/journalctl
- Fix postqueue: remove -p flag (conflicts with -j)
- Add stderr logging for queue errors

backend/internal/api/handlers/queue.go

@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"log"
 	"net/http"
 
 	"github.com/imc-vibe/backend/internal/mail"
@@ -20,7 +21,8 @@ func (h *QueueHandler) List(w http.ResponseWriter, r *http.Request) {
 
 	entries, err := mail.GetQueue()
 	if err != nil {
-		Error(w, http.StatusServiceUnavailable, "mail queue tools not available")
+		log.Printf("Queue error: %v", err)
+		Error(w, http.StatusServiceUnavailable, "failed to get queue: "+err.Error())
 		return
 	}