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/sharing-links.html

@@ -0,0 +1,17 @@
+{{ with .Params.sharingLinks | default (.Site.Params.article.sharingLinks | default false) }}
+  {{ $links := hugo.Data.sharing }}
+  <section class="flex flex-row flex-wrap justify-center pt-4 text-xl">
+    {{ range . }}
+      {{ with index $links . }}
+        <a
+          class="m-1 rounded bg-neutral-300 p-1.5 text-neutral-700 hover:bg-primary-500 hover:text-neutral dark:bg-neutral-700 dark:text-neutral-300 dark:hover:bg-primary-400 dark:hover:text-neutral-800"
+          target="_blank"
+          href="{{ printf .url $.Permalink $.Title | safeURL }}"
+          title="{{ i18n .title }}"
+          aria-label="{{ i18n .title }}">
+          {{ partial "icon.html" .icon }}
+        </a>
+      {{ end }}
+    {{ end }}
+  </section>
+{{ end }}