migrate to decoupled Blowfish layout, fix TOC scrollspy, and update docs

- Theme Decoupling & Cleanup:
      - Fully decoupled and vendored the Blowfish theme directly into root directories (layouts/,
  assets/, static/, data/, i18n/).
      - De-registered and cleaned up legacy Git submodules (themes/blowfish, themes/hugo-admonitions)
  from the Git index to protect the build from upstream breakages.
      - Configured .gitignore to ignore development preview symlinks (content, static,
  config/_default/menus.en.toml), build folders (public/, resources/), and locks.

    - TOC & Layout Fixes:
      - Replaced the custom layouts/_default/single.html template with the Blowfish default to restore
  native container widths and the side-by-side flex layout.
      - Restored TOC to float on the right sidebar on desktop viewports and render inline on mobile
  viewports.
      - Fixed a parameter resolution bug in layouts/partials/toc.html by checking both .Site.Params.
  smartTOC and .Site.Params.article.smartTOC (where it is defined in params.toml).
      - Upgraded the TOC scrollspy JavaScript to target all '#TableOfContents' containers on the page,
  enabling highlight tracking on both desktop and mobile layouts.

    - Documentation Updates (README.md):
      - Restored YAML front matter metadata block at the top.
      - Added detailed notes on the CI/CD build process and Gitea runner deployment targets
  (/srv/www/docs-public and /srv/www/docs-private).
      - Added a categorized and sorted "Shortcodes Quick Reference" table at the top of the shortcodes
  section (ordered by Custom, Hugo Default, and Blowfish).
      - Documented custom shortcodes (Include, Screenshot, Raw HTML) and missing Hugo default
  shortcodes (Highlight, Instagram, Param, Ref, Relref, Twitter, Vimeo, Youtube).
      - Restructured headings to ensure all sub-shortcodes are H3, removed block break tags (<br/>),
  and appended horizontal separators (---) after H2 sections.

i18n/de.yaml

@@ -0,0 +1,88 @@
+global:
+  language: "DE"
+
+article:
+  anchor_label: "Anker"
+  date: "{{ .Date }}"
+  date_updated: "Aktualisiert: {{ .Date }}"
+  draft: "Entwurf"
+  edit_title: "Inhalt bearbeiten"
+  reading_time:
+    one: "{{ .Count }} min"
+    other: "{{ .Count }} min"
+  reading_time_title: "Lesezeit"
+  table_of_contents: "Inhaltsverzeichnis"
+  word_count:
+    one: "{{ .Count }} Wort"
+    other: "{{ .Count }} Wörter"
+  views:
+    one: "{{ .Count }} Ansicht"
+    other: "{{ .Count }} Ansichten"
+  likes:
+    one: "{{ .Count }} Like"
+    other: "{{ .Count }} Likes"
+  part_of_series: "Dieser Artikel ist Teil einer Serie."
+  part: "Teil"
+  this_article: "Dieser Artikel"
+  related_articles: "Verwandte Artikel"
+  reply_by_email: "Per E-Mail antworten"
+  reply_to: "Antwort auf {{ .Title }}"
+  zen_mode_title:
+    enable: "Zen-Modus aktivieren"
+    disable: "Zen-Modus deaktivieren"
+
+a11y:
+  title: "Einstellungen zur Barrierefreiheit"
+  disable_blur: "Blur deaktivieren"
+  disable_images: "Bilder deaktivieren"
+  show_link_underline: "Links unterstreichen"
+  font_size: "Schriftgröße"
+
+author:
+  byline_title: "Autor"
+
+code:
+  copy: "Kopieren"
+  copied: "Kopiert"
+
+error:
+  404_title: "Seite nicht gefunden :confused:"
+  404_error: "Fehler 404"
+  404_description: "Es sieht so aus, als ob es diese Seite nicht gibt."
+
+footer:
+  dark_appearance: "Zum dunklen Erscheinungsbild wechseln"
+  light_appearance: "Zum hellen Erscheinungsbild wechseln"
+  powered_by: "Erstellt mit {{ .Hugo }} & {{ .Theme }}"
+
+list:
+  externalurl_title: "Link zu einer externen Seite"
+  no_articles: "Es gibt hier noch keine Beiträge."
+
+nav:
+  scroll_to_top_title: "Zum Anfang scrollen"
+  skip_to_main: "Zum Hauptinhalt springen"
+
+search:
+  open_button_title: "Suche (/)"
+  close_button_title: "Schließen (Esc)"
+  input_placeholder: "Suchen"
+
+sharing:
+  email: "Per E-Mail teilen"
+  facebook: "Auf Facebook teilen"
+  line: "Auf LINE teilen"
+  linkedin: "Auf LinkedIn teilen"
+  pinterest: "Auf Pinterest pinnen"
+  reddit: "An Reddit senden"
+  twitter: "Auf Twitter teilen"
+  bluesky: "Auf Bluesky posten"
+  whatsapp: "Über WhatsApp teilen"
+  telegram: "Über Telegram teilen"
+  mastodon: "Auf Mastodon teilen"
+
+shortcode:
+  recent_articles: "Neue Beiträge"
+
+recent:
+  show_more: "Zeige Mehr"