i18n(comments): all UI strings through translations

Pulls every German string out of Comments.svelte, PostCard.svelte and
CommentCountBadge.svelte and routes it through `useTranslate()` +
the `T.*` key registry. New keys (`comments_*`, `post_overview` count
aria, `comments_jump_to`) are registered in `lib/translations.ts`.

Default DE values land in
`cms_content/windwiderstand/de/translation_bundle/app.json5` (committed
separately) so the CMS-loaded bundle keeps the same look without each
component falling back to its raw key.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/lib/components/PostCard.svelte

@@ -6,6 +6,9 @@
   import EventBadges from "./EventBadges.svelte";
   import RustyImage from "./RustyImage.svelte";
   import Card from "./Card.svelte";
+  import { useTranslate, T } from "$lib/translations";
+
+  const t = useTranslate();
 
   type PostWithImage = PostEntry & {
     _resolvedImageUrl?: string;
@@ -98,8 +101,8 @@
       <div class="absolute top-2 left-2">
         <span
           class="inline-flex items-center gap-1 rounded-full bg-white/90 px-2 py-1 text-[.65rem] font-semibold tabular-nums text-zinc-700 shadow-sm"
-          aria-label="{commentCount} Kommentare"
-          title="{commentCount} Kommentare"
+          aria-label={t(T.comments_count_aria, { count: commentCount })}
+          title={t(T.comments_count_aria, { count: commentCount })}
         >
           <Icon icon="mdi:comment-outline" class="size-3" />
           {commentCount}