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/partials/header/components/translations.html

@@ -0,0 +1,23 @@
+{{ if .IsTranslated }}
+  <div class="translation nested-menu">
+    <button class="cursor-pointer flex items-center">
+      <span class="me-1">
+        {{ partial "icon.html" "language" }}
+      </span>
+      <span class="text-sm font-medium bf-icon-color-hover" title="{{ .Title }}">
+        {{- i18n "global.language" | markdownify -}}
+      </span>
+    </button>
+    <ul class="menuhide">
+      <li class="rounded-xl backdrop-blur shadow-2xl p-2 flex flex-col gap-1">
+        {{ range .AllTranslations }}
+          <a href="{{ .RelPermalink }}" class="flex items-center bf-icon-color-hover px-3 py-1">
+            <span class="text-sm font-sm" title="{{ .Title }}">
+              {{ .Language.Params.displayName | emojify }}
+            </span>
+          </a>
+        {{ end }}
+      </li>
+    </ul>
+  </div>
+{{ end }}