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/nl.yaml

@@ -0,0 +1,83 @@
+global:
+  language: "NL"
+
+article:
+  anchor_label: "Anker"
+  date: "{{ .Date }}"
+  date_updated: "Bijgewerk: {{ .Date }}"
+  draft: "Concept"
+  edit_title: "Inhoud bewerken"
+  reading_time:
+    one: "{{ .Count }} min"
+    other: "{{ .Count }} mins"
+  reading_time_title: "Leestijd"
+  table_of_contents: "Inhoudsopgave"
+  word_count:
+    one: "{{ .Count }} woord"
+    other: "{{ .Count }} woorden"
+  views:
+    one: "{{ .Count }} uitzicht"
+    other: "{{ .Count }} uitzichten"
+  likes:
+    one: "{{ .Count }} leuk"
+    other: "{{ .Count }} leuk"
+  part_of_series: "Dit artikel is onderdeel van een serie."
+  part: "Deel"
+  this_article: "Dit artikel"
+  related_articles: "Gerelateerde artikelen"
+  reply_by_email: "Reageren via email"
+  reply_to: "Reactie op {{ .Title }}"
+  zen_mode_title:
+    enable: "Zen-modus inschakelen"
+    disable: "Zen-modus uitschakelen"
+
+a11y:
+  title: "Toegankelijkheidsinstellingen"
+
+author:
+  byline_title: "Auteur"
+
+code:
+  copy: "Kopiëren"
+  copied: "Gekopieerd"
+
+error:
+  404_title: "Pagina niet gevonden :confused:"
+  404_error: "Error 404"
+  404_description: "De pagina die je zoekt, is niet gevonden."
+
+footer:
+  dark_appearance: "Schakel over naar donkere weergave"
+  light_appearance: "Schakel over naar lichte weergave"
+  powered_by: "Aangedreven door {{ .Hugo }} & {{ .Theme }}"
+
+list:
+  externalurl_title: "Externe link"
+  no_articles: "Er zijn nog geen artikelen om hier te vermelden."
+
+nav:
+  scroll_to_top_title: "Scroll naar boven"
+  skip_to_main: "Naar de hoofdinhoud gaan"
+
+search:
+  open_button_title: "Zoeken (/)"
+  close_button_title: "Sluiten (Esc)"
+  input_placeholder: "Zoeken"
+
+sharing:
+  email: "Delen via email"
+  facebook: "Delen op Facebook"
+  line: "Delen op LINE"
+  linkedin: "Delen op LinkedIn"
+  pinterest: "Delen op Pinterest"
+  reddit: "Indienen op Reddit"
+  twitter: "Delen op X"
+  bluesky: "Delen op Bluesky"
+  whatsapp: "Delen op WhatsApp"
+  telegram: "Delen op Telegram"
+
+shortcode:
+  recent_articles: "Recente"
+
+recent:
+  show_more: "Meer tonen"