Initial commit: Astro 6 static blog site

- German (default) and English i18n support
- Categories and tags
- Blog posts with hero images
- Dark/light theme switcher
- View Transitions removed to fix reload ghost images
- Webmentions integration
- RSS feeds per locale

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

compose.yml

@@ -0,0 +1,13 @@
+name: adrian-altner-de
+
+services:
+  website:
+    image: localhost/adrian-altner.de:latest
+    container_name: adrian-altner.de
+    ports:
+      - "4321:4321"
+    environment:
+      NODE_ENV: production
+      HOST: 0.0.0.0
+      PORT: 4321
+    restart: unless-stopped