Add staff-only all comments page and bump versions

- Add new "alle-kommentare" (all comments) view for staff users only
  - Allows staff to view and manage all user comments across the system
  - Grouped by document with user information displayed
  - Staff can delete any comment via the dedicated delete button
  - Restricts access via user_passes_test decorator

- Create all_comments.html template
  - Based on user_comments template with added username field
  - Shows comment author, creation time, and edit time
  - Provides delete functionality for comment management

- Update navigation menu
  - Add "Alle Kommentare" link in user dropdown menu
  - Link only visible to staff members

- Add URL route for alle-kommentare page
  - Path: /dokumente/alle-kommentare/
  - URL name: all_comments

- Bump application versions
  - Update footer version from 0.965 to 0.966
  - Update K8s deployment version from 0.917 to 0.918
  - ArgoCD deployment already at 0.966

All existing tests pass (148 tests total)

argocd/deployment.yaml

@@ -25,7 +25,7 @@ spec:
               mountPath: /data
       containers:
         - name: web
-          image: git.baumann.gr/adebaumann/vui:0.965
+          image: git.baumann.gr/adebaumann/vui:0.966
           imagePullPolicy: Always
           ports:
             - containerPort: 8000