Initial SvelteKit frontend port of windwiderstand.de

Full parity with Astro site: content rows, post/tag routes, pagination,
event badges + OSM map, comments, Live-Search via /api/search-index,
CMS image proxy, RSS, sitemap.

Deploy: Dockerfile + docker-compose.prod.yml + Gitea Actions workflow
to build + push to git.pm86.de registry and ssh-deploy to Contabo.

docker-compose.prod.yml

@@ -0,0 +1,20 @@
+services:
+  windwiderstand:
+    image: git.pm86.de/admin/windwiderstand:latest
+    container_name: windwiderstand
+    restart: unless-stopped
+    expose:
+      - "3001"
+    env_file: /opt/windwiderstand/.env
+    volumes:
+      - image-cache:/data/image-cache
+    networks:
+      - web
+
+volumes:
+  image-cache:
+
+networks:
+  web:
+    external: true
+    name: stacks_web