Webapp: Updates pages, image page tabs with review-before-save, BPRT sync

Updates group:
- Dell drivers and BIOS: check Dell's catalogs against all three driver maps
  and models.txt, download with a shared speed cap, repack, preview, apply
  with backups and rollback.
- iPXE boot files: check GitHub for the signed Secure Boot set, verify the
  sha256 and each file's signer, install atomically, roll back. Includes the
  by-hand procedure.
- Blancco: upload a release, stage it, test-boot it from the menu, activate,
  roll back.
- BPRT sync: validate a batch uploaded from the MediaCreator Lite cache
  (scripts/windows/Sync-BPRT.ps1 or a zip), show the diff, swap with the site
  overlay files kept.

Images: one sidebar entry per image with Overview, Drivers, Unattend and OS and
Packages tabs. Every save shows a diff first, keeps the file's format, makes a
backup and can be undone. Driver lint runs inline.

Enrollment: upload standard/engineer MCL packages, one per tenant/purpose,
with archive and restore. Hardware coverage counts engineer as Win11.

webapp/templates/dashboard.html

@@ -119,9 +119,9 @@
             </td>
             <td><span class="mono">{{ img.deploy_path }}</span></td>
             <td class="actions text-end">
-              <a href="{{ url_for('image_config', image_type=img.image_type) }}"
+              <a href="{{ image_tab_url(img.image_type, 'overview') }}"
                  class="btn btn-sm btn-outline-secondary btn-row-action">
-                <i class="bi bi-gear"></i> Config
+                <i class="bi bi-clipboard-data"></i> Open
               </a>
               <a href="{{ url_for('unattend_editor', image_type=img.image_type) }}"
                  class="btn btn-sm btn-outline-primary btn-row-action">