feat: switch to PaperMod theme, add Rybbit analytics, CI/CD deploy

- Replace ananke with PaperMod theme (git submodule)
- Configure PaperMod: reading time, breadcrumbs, search, dark mode
- Localize menus for EN/DE
- Register internetforkids.ong in Rybbit (site ID: a0ab05916d6c)
- Migrate partials from ananke _partials/ to PaperMod extend_head/footer
- Set up webhook-based auto-deploy on push to main

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

layouts/partials/extend_footer.html

@@ -0,0 +1,2 @@
+{{/* Rybbit privacy-friendly analytics */}}
+{{ partial "rybbit.html" . }}