Webapp redesign phase 6: the remaining pages

Restyled to the same row pattern (one line, details in an expandable
body, one action plus a menu, tokens for light and dark):
- hardware coverage, audit log (family chips, destructive actions in
  red, client-side filters, first 300 rows), Clonezilla backups,
  enrollment packages (active package marked and undeletable, MCL flags
  with a visible legend)
- image Overview, OS and packages, Unattend (sticky save bar), Import
- Dell, iPXE, Blancco and BPRT update pages; Dell history links to the
  rollback review instead of rolling back on one click
- boot menu editor (tabs, rows with a menu, lint chips that jump to the
  line, tokens instead of hard-coded dark colours) and the imaging
  session detail page

Fixes found on the way:
- BPRT batch Activate never asked to confirm: a hidden input named
  'confirm' shadowed window.confirm in the inline handler, so the form
  submitted without a prompt. It now calls window.confirm.
- Backup upload refused when a backup with that name exists, unless
  'Replace the existing backup' is ticked (it overwrote silently).
- app.js: em dashes in comments replaced (plain ASCII).

webapp/app.py

@@ -560,6 +560,10 @@ def clonezilla_upload():
 
     os.makedirs(config.CLONEZILLA_SHARE, exist_ok=True)
     dest = os.path.join(config.CLONEZILLA_SHARE, filename)
+    # A backup is a whole disk image: never replace one by accident.
+    if os.path.exists(dest) and request.form.get("overwrite") != "1":
+        flash(f"{filename} already exists. Tick Replace the existing backup to overwrite it.", "danger")
+        return redirect(url_for("clonezilla_backups"))
     f.save(dest)
     audit("BACKUP_UPLOAD", filename)
     flash(f"Uploaded {filename} successfully.", "success")