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/breadcrumbs.html

@@ -0,0 +1,19 @@
+<ol class="text-sm text-neutral-500 dark:text-neutral-400 print:hidden">
+  {{ template "crumb" (dict "p1" . "p2" .) }}
+</ol>
+{{ define "crumb" }}
+  {{ if .p1.Parent }}
+    {{ template "crumb" (dict "p1" .p1.Parent "p2" .p2 ) }}
+  {{ else if not .p1.IsHome }}
+    {{ template "crumb" (dict "p1" .p1.Site.Home "p2" .p2 ) }}
+  {{ end }}
+  <li class="{{ if or (eq .p1 .p2) (.p1.IsHome) }}hidden{{ else }}inline{{ end }}">
+    <a class="hover:underline decoration-neutral-300 dark:underline-neutral-600" href="{{ .p1.RelPermalink }}"
+      >{{ if .p1.Title }}
+        {{- .p1.Title -}}
+      {{ else }}
+        {{- .p1.Section -}}
+      {{ end }}</a
+    ><span class="px-1 text-primary-500">/</span>
+  </li>
+{{ end }}