Fix: Samba MacOS toggle deaktivieren löscht fruit: Keys via delparm

net conf setparm kann Keys nicht entfernen. Beim Deaktivieren blieben
fruit:* Keys in der Registry erhalten. Jetzt werden Keys die im neuen
Dict fehlen via net conf delparm gelöscht.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/services/shares.py

@@ -251,8 +251,20 @@ class SharesManager:
             return {"parameters": []}
 
     def set_samba_global_config(self, parameters: Dict[str, str]) -> bool:
-        """Update Samba global configuration parameters using 'net conf setparm'"""
+        """Update Samba global configuration parameters using 'net conf setparm/delparm'"""
         try:
+            current = self.get_samba_global_config()
+            current_keys = {p["key"] for p in current.get("parameters", [])}
+            new_keys = set(parameters.keys())
+
+            # Delete keys that were removed
+            for key in current_keys - new_keys:
+                subprocess.run(
+                    ['/usr/bin/net', 'conf', 'delparm', 'global', key],
+                    capture_output=True, text=True, timeout=10
+                )
+
+            # Set/update remaining keys
             for key, value in parameters.items():
                 result = subprocess.run(
                     ['/usr/bin/net', 'conf', 'setparm', 'global', key, '--', value],