feat(comments): hide every comment mention when COMMENTS_ENABLED=false

The kill-switch previously left comment UI/text visible in several places.
Sweep the whole surface so a comments-off instance shows no trace:

Frontend (main app):
- VirtualFeed grid tile: gate the comment button/count on $commentsEnabled
  (was ungated — the only feed surface still showing it).
- admin stats: hide the "Kommentare" count card.
- UploadSheet "Uploads geschlossen" notice, host ban-modal description, and
  host/admin unban confirmations: drop the "…und kommentieren" wording.
- export page: drop "Kommentaren" from the keepsake description.

Keepsake export (had no concept of the flag):
- export.rs: thread comments_enabled into the exported data (ViewerEvent),
  wired through spawn_export_jobs/recover_exports and their call sites
  (host.rs, main.rs).
- export-viewer: gate comment counts (list + grid) and the lightbox comments
  section; older exports without the field default to enabled (?? true).

Backend still 403s comment writes when disabled (unchanged) — this is the UI
half so stale clients and archives match.

Verified on the running stack (COMMENTS_ENABLED=false): /event reports
comments_enabled=false, a regenerated keepsake embeds "comments_enabled": false
with no comment UI, and the uploads-closed notice renders "…ansehen und liken."

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/components/UploadSheet.svelte

@@ -6,6 +6,7 @@
 	import CameraCapture from '$lib/components/CameraCapture.svelte';
 	import type { PendingFile } from '$lib/pending-upload-store';
 	import { eventState, uploadsClosed } from '$lib/event-state-store';
+	import { commentsEnabled } from '$lib/event-config-store';
 
 	// Uploads closed (event locked or gallery released) — show a lock notice instead of
 	// the capture options, so a guest can't stage a photo that would just be rejected.
@@ -163,8 +164,9 @@
 			<div class="rounded-xl bg-amber-50 px-5 py-4 text-center dark:bg-amber-950/30">
 				<p class="font-semibold text-amber-800 dark:text-amber-300">Uploads geschlossen</p>
 				<p class="mt-1 text-sm text-amber-700 dark:text-amber-400">
-					Der Host hat die Uploads für dieses Event beendet. Du kannst weiterhin Fotos ansehen,
-					liken und kommentieren.
+					Der Host hat die Uploads für dieses Event beendet. Du kannst weiterhin Fotos ansehen{$commentsEnabled
+						? ', liken und kommentieren'
+						: ' und liken'}.
 				</p>
 			</div>
 			<button onclick={close} class="btn btn-secondary btn-block"> Schließen </button>

frontend/src/lib/components/VirtualFeed.svelte

@@ -22,6 +22,7 @@
 	import { browser } from '$app/environment';
 	import type { FeedUpload } from '$lib/types';
 	import { dataMode } from '$lib/data-mode-store';
+	import { commentsEnabled } from '$lib/event-config-store';
 	import { longpress } from '$lib/actions/longpress';
 	import FeedListCard from './FeedListCard.svelte';
 
@@ -277,24 +278,31 @@
 												</svg>
 												{upload.like_count}
 											</button>
-											<button
-												class="pointer-events-auto -m-1 flex items-center gap-0.5 p-1"
-												onclick={(e) => {
-													e.stopPropagation();
-													oncomment(upload.id);
-												}}
-												aria-label="Kommentare anzeigen"
-											>
-												<svg class="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor">
-													<path
-														stroke-linecap="round"
-														stroke-linejoin="round"
-														stroke-width="2"
-														d="M8 12h.01M12 12h.01M16 12h.01M21 12c0 4.418-4.03 8-9 8a9.863 9.863 0 01-4.255-.949L3 20l1.395-3.72C3.512 15.042 3 13.574 3 12c0-4.418 4.03-8 9-8s9 3.582 9 8z"
-													/>
-												</svg>
-												{upload.comment_count}
-											</button>
+											{#if $commentsEnabled}
+												<button
+													class="pointer-events-auto -m-1 flex items-center gap-0.5 p-1"
+													onclick={(e) => {
+														e.stopPropagation();
+														oncomment(upload.id);
+													}}
+													aria-label="Kommentare anzeigen"
+												>
+													<svg
+														class="h-4 w-4"
+														fill="none"
+														viewBox="0 0 24 24"
+														stroke="currentColor"
+													>
+														<path
+															stroke-linecap="round"
+															stroke-linejoin="round"
+															stroke-width="2"
+															d="M8 12h.01M12 12h.01M16 12h.01M21 12c0 4.418-4.03 8-9 8a9.863 9.863 0 01-4.255-.949L3 20l1.395-3.72C3.512 15.042 3 13.574 3 12c0-4.418 4.03-8 9-8s9 3.582 9 8z"
+														/>
+													</svg>
+													{upload.comment_count}
+												</button>
+											{/if}
 										</div>
 									</div>
 								</div>