fix(nextcloud-files): CR-02 Nextcloud-Adresse aendern nur noch Administratoren

- PUT settings traegt @Roles(ADMIN, SUPER_ADMIN) statt @ModuleManage (Muster wie
  TendersController.getSourceConfig); alle Benutzer schicken ihr Passwort an diese Adresse
- POST settings/test: Verwalter ohne Administratorrolle pruefen nur die gespeicherte Adresse,
  jede andere Adresse ist 403
- Einstellungen fuer Verwalter nur lesbar mit kurzem Hinweis, ohne Speichern-Knopf; Hinweis
  "nicht eingerichtet" verweist Nicht-Administratoren an einen Administrator
- Metadaten-Spec (module-manage-handlers), Controller-Spec, Seitentest, e2e-settings
  (Verwalter: 403 auf PUT und fremde Pruefung), Anleitungen und Changelog angepasst

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

apps/web/src/messages/en.json

@@ -2331,7 +2331,7 @@
     "notConfigured": {
       "title": "Nextcloud has not been set up yet.",
       "managerHint": "Enter the address of your Nextcloud in the settings.",
-      "userHint": "Please contact an administrator or someone with the Manage permission level.",
+      "userHint": "Please contact an administrator. Only an administrator can enter the Nextcloud address.",
       "goToSettings": "Go to settings"
     },
     "connect": {
@@ -2390,7 +2390,8 @@
         "placeholder": "https://cloud.your-company.com",
         "test": "Check connection",
         "testing": "Checking …",
-        "connectedUsers": "{count, plural, =0 {Nobody is connected right now.} one {One user is connected.} other {# users are connected.}}"
+        "connectedUsers": "{count, plural, =0 {Nobody is connected right now.} one {One user is connected.} other {# users are connected.}}",
+        "adminOnly": "The address is set by an administrator. You can view it here and check the connection."
       },
       "reconnect": {
         "message": "{count, plural, one {One user is connected. After the change they have to sign in again.} other {# users are connected. After the change everyone has to sign in again.}}",