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.

layouts/shortcodes/accordionItem.html

@@ -0,0 +1,38 @@
+{{ $parent := .Parent }}
+{{ $separated := false }}
+{{ if $parent }}
+  {{ $separated = $parent.Get "separated" | default false }}
+{{ end }}
+{{ $isSeparated := or (eq $separated true) (eq $separated "true") }}
+
+{{ $title := .Get "title" | default (.Get "header") }}
+{{ $icon := .Get "icon" }}
+{{ $md := .Get "md" | default true }}
+{{ $open := .Get "open" | default false }}
+{{ $isOpen := or (eq $open true) (eq $open "true") }}
+{{ $align := .Get "align" }}
+
+<details
+  class="group {{ if $isSeparated }}rounded-lg border border-neutral-200 dark:border-neutral-700 overflow-hidden{{ else }}border-none{{ end }}"
+  data-accordion-item
+  {{ if $isOpen }}open{{ end }}
+>
+  <summary class="flex w-full cursor-pointer items-center justify-between gap-4 px-4 py-3 text-left text-lg font-semibold text-neutral-900 dark:text-neutral-100">
+    <span class="flex items-center gap-2">
+      {{ with $icon }}
+        {{ partial "icon.html" . }}
+      {{ end }}
+      <span>{{ $title }}</span>
+    </span>
+    <span class="accordion-chevron ms-auto flex h-5 w-5 items-center justify-center print:hidden">
+      {{ partial "icon.html" "chevron-down" }}
+    </span>
+  </summary>
+<div class="px-4 pb-4 text-neutral-700 dark:text-neutral-300{{ if $align }} text-{{ $align }}{{ end }}">
+    {{ if $md }}
+      {{- .Inner | markdownify -}}
+    {{ else }}
+      {{- .Inner -}}
+    {{ end }}
+  </div>
+</details>