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/article-link/card-related.html

@@ -0,0 +1,104 @@
+{{/* Used by
+  1. layouts/partials/related.html (related articles in single page)
+*/}}
+{{ $disableImageOptimization := site.Store.Get "disableImageOptimization" }}
+
+{{ $page := .Page }}
+{{ $featured := "" }}
+{{ $featuredURL := "" }}
+{{ $thumbnailAspectRatio := site.Params.thumbnailAspectRatio | default "1.5" }}
+{{ $thumbnailAspectRatio = replaceRE "[^0-9.]" "" $thumbnailAspectRatio }}
+{{ if eq $thumbnailAspectRatio "" }}{{ $thumbnailAspectRatio = "1.5" }}{{ end }}
+{{/* frontmatter */}}
+{{ with $page }}
+  {{ with .Params.featureimage }}
+    {{ if or (strings.HasPrefix . "http:") (strings.HasPrefix . "https:") }}
+      {{ if site.Params.hotlinkFeatureImage }}
+        {{ $featuredURL = . }}
+      {{ else }}
+        {{ $featured = resources.GetRemote . }}
+      {{ end }}
+    {{ else }}
+      {{ $featured = resources.Get . }}
+    {{ end }}
+  {{ end }}
+
+  {{/* page resources */}}
+  {{ if not (or $featured $featuredURL) }}
+    {{ $images := .Resources.ByType "image" }}
+    {{ range slice "*feature*" "*cover*" "*thumbnail*" }}
+      {{ if not $featured }}{{ $featured = $images.GetMatch . }}{{ end }}
+    {{ end }}
+  {{ end }}
+
+  {{/* fallback to default */}}
+  {{ if not (or $featured $featuredURL) }}
+    {{ $default := site.Store.Get "defaultFeaturedImage" }}
+    {{ if $default.url }}
+      {{ $featuredURL = $default.url }}
+    {{ else if $default.obj }}
+      {{ $featured = $default.obj }}
+    {{ end }}
+  {{ end }}
+
+  {{/* generate image URL if not hotlink */}}
+  {{ if not $featuredURL }}
+    {{ with $featured }}
+      {{ $featuredURL = .RelPermalink }}
+      {{ if not (or $disableImageOptimization (eq .MediaType.SubType "svg")) }}
+        {{ $featuredURL = (.Resize "600x").RelPermalink }}
+      {{ end }}
+    {{ end }}
+  {{ end }}
+{{ end }}
+
+
+<article
+  class="article-link--related relative min-h-full min-w-full overflow-hidden rounded-lg border border-neutral-300 dark:border-neutral-600">
+  {{ with $featuredURL }}
+    <div class="flex-none relative overflow-hidden thumbnail_card_related" style="--thumbnail-aspect-ratio: {{ $thumbnailAspectRatio }}">
+      <img
+        src="{{ . }}"
+        role="presentation"
+        loading="lazy"
+        decoding="async"
+        fetchpriority="low"
+        class="not-prose absolute inset-0 w-full h-full object-cover">
+    </div>
+  {{ end }}
+  {{ if and .Draft .Site.Params.article.showDraftLabel }}
+    <span class="absolute top-0 right-0 m-2">
+      {{ partial "badge.html" (i18n "article.draft" | emojify) }}
+    </span>
+  {{ end }}
+  <div class="p-4">
+    <header>
+      <a
+        {{ with $page.Params.externalUrl }}
+          href="{{ . }}" target="_blank" rel="external"
+        {{ else }}
+          href="{{ $page.RelPermalink }}"
+        {{ end }}
+        class="not-prose before:absolute before:inset-0 decoration-primary-500 dark:text-neutral text-xl font-bold text-neutral-800 hover:underline hover:underline-offset-2">
+        <h2>
+          {{ .Title | emojify }}
+          {{ if .Params.externalUrl }}
+            <span class="cursor-default align-top text-xs text-neutral-400 dark:text-neutral-500">
+              <span class="rtl:hidden">&#8599;</span>
+              <span class="ltr:hidden">&#8598;</span>
+            </span>
+          {{ end }}
+        </h2>
+      </a>
+    </header>
+    <div class="text-sm text-neutral-500 dark:text-neutral-400">
+      {{ partial "article-meta/basic.html" . }}
+    </div>
+    {{ if .Params.showSummary | default (.Site.Params.list.showSummary | default false) }}
+      <div class="article-link__summary prose dark:prose-invert mt-1 line-clamp-5">
+        {{ .Summary | plainify }}
+      </div>
+    {{ end }}
+  </div>
+  <div class="px-6 pt-4 pb-2"></div>
+</article>