Nginx-UI: better User Handling | ACME (#11715)

* fix(nginx-ui): remove admin user hack, use setup wizard instead

The previous install script started nginx-ui for 3 seconds, stopped it,
and ran reset-password to create an admin user. This caused:
- Race condition: the internal setup wizard could trigger during the brief
  start window, conflicting with the reset-password approach
- Admin users unable to login after the setup wizard fired
- Settings lockup due to overloaded app.ini with hardcoded nginx paths
  that conflict with UI-managed settings

Changes:
- Remove start/stop/reset-password hack from install script
- Simplify app.ini to match upstream defaults (minimal config)
- Let users complete the natural setup wizard on first visit
- Update JSON: remove default credentials, add setup wizard note
- Add setup wizard hint to CT script output

The setup wizard properly handles admin account creation and ACME email
configuration, which are both needed for full functionality.

Ref: ProxmoxVED#1408

* Update nginx-ui.sh

frontend/public/json/nginx-ui.json

@@ -28,10 +28,14 @@
         }
     ],
     "default_credentials": {
-        "username": "admin",
+        "username": null,
         "password": null
     },
     "notes": [
+        {
+            "text": "On first visit, the setup wizard will guide you to create an admin account and configure ACME email.",
+            "type": "warning"
+        },
         {
             "text": "Nginx runs on ports 80/443, Nginx UI management interface on port 9000.",
             "type": "info"
@@ -39,10 +43,6 @@
         {
             "text": "SSL certificates can be managed automatically with Let's Encrypt integration.",
             "type": "info"
-        },
-        {
-            "text": "Initial Login data: `cat ~/nginx-ui.creds`",
-            "type": "info"
         }
     ]
 }