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>

tsconfig.json

@@ -0,0 +1,11 @@
+{
+  "extends": "astro/tsconfigs/strict",
+  "include": [".astro/types.d.ts", "**/*"],
+  "exclude": ["dist"],
+  "compilerOptions": {
+    "strictNullChecks": true,
+    "paths": {
+      "~/*": ["./src/*"]
+    }
+  }
+}