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/gallery.html

@@ -0,0 +1,31 @@
+{{ $id := delimit (slice "gallery" (partial "functions/uid.html" .)) "-" -}}
+{{ $content := .Inner -}}
+
+{{/* find all img tags */}}
+{{ range findRE `<img\s+[^>]*>` $content -}}
+  {{ $imgTag := . -}}
+  {{/* extract src attribute */}}
+  {{ with findRESubmatch `src=['"]([^'"]+)['"]` $imgTag -}}
+    {{ $srcAttr := index (index . 0) 0 -}}
+    {{ $srcValue := index (index . 0) 1 -}}
+    {{ $srcValueFinal := $srcValue -}}
+
+    {{ if or (hasPrefix $srcValue "http://") (hasPrefix $srcValue "https://") -}}
+      {{ with resources.GetRemote $srcValue -}}{{ $srcValueFinal = .RelPermalink -}}{{ end -}}
+    {{ else -}}
+      {{ with $.Page.Resources.GetMatch $srcValue -}}
+        {{ $srcValueFinal = .RelPermalink -}}
+      {{ else -}}
+        {{ with resources.GetMatch $srcValue -}}{{ $srcValueFinal = .RelPermalink -}}{{ end -}}
+      {{ end -}}
+    {{ end -}}
+
+    {{ $newTag := replace $imgTag $srcAttr (printf `src="%s"` $srcValueFinal) -}}
+    {{ $content = replace $content $imgTag $newTag -}}
+  {{ end -}}
+{{ end -}}
+
+{{ if not .Parent }}<div class="width-patch"></div>{{ end }}
+<div id="{{- $id -}}" class="gallery">
+  {{ $content | safeHTML -}}
+</div>