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/home/card.html

@@ -0,0 +1,53 @@
+<div class="relative pt-16 pb-32">
+  <div aria-hidden="true" class="absolute inset-x-0 top-0 h-48 bg-gradient-to-b"></div>
+  <div class="relative">
+    <div class="lg:mx-auto lg:grid lg:max-w-7xl lg:grid-flow-col-dense lg:grid-cols-2 lg:gap-24 lg:px-8">
+      <div class="mx-auto max-w-xl px-4 sm:px-6 lg:mx-0 lg:max-w-none lg:py-16 lg:px-0">
+        <article class="max-w-full prose dark:prose-invert">
+          {{ with .Title }}
+            <header>
+              <h1>{{ . | emojify }}</h1>
+            </header>
+          {{ end }}
+          <section class="w-full">{{ .Content }}</section>
+        </article>
+      </div>
+      <div class="mt-6 sm:mt-16 lg:mt-0 mx-auto max-w-xl px-4 sm:px-6 lg:mx-0 lg:max-w-none lg:py-16 lg:px-0">
+        <div class="-me-48 md:-me-16 lg:relative lg:m-0 lg:h-full lg:px-0 w-full">
+          {{ $useDefault := true }}
+          {{ $homepageImage := "" }}
+          {{ with .Site.Params.defaultBackgroundImage }}
+            {{ if or (strings.HasPrefix . "http:") (strings.HasPrefix . "https:") }}
+              {{ $homepageImage = resources.GetRemote . }}
+            {{ else }}
+              {{ $homepageImage = resources.Get . }}
+            {{ end }}
+          {{ end }}
+          {{ with .Site.Params.homepage.homepageImage }}
+            {{ if or (strings.HasPrefix . "http:") (strings.HasPrefix . "https:") }}
+              {{ $homepageImage = resources.GetRemote . }}
+              {{ $useDefault = false }}
+            {{ else }}
+              {{ $homepageImage = resources.Get . }}
+              {{ $useDefault = false }}
+            {{ end }}
+          {{ end }}
+          {{ if $homepageImage }}
+            {{ $style := "" }}
+            {{ $defaultPosition := cond $useDefault site.Params.imagePosition false }}
+            {{ with $.Params.imagePosition | default $defaultPosition }}
+              {{ $style = printf "object-position: %s;" . }}
+            {{ end }}
+            <img
+              class="w-full rounded-xl shadow-xl lg:absolute lg:h-full lg:w-auto lg:max-w-none"
+              src="{{ $homepageImage.RelPermalink }}"
+              {{ if $style }}style="{{ $style | safeCSS }}"{{ end }}>
+          {{ end }}
+        </div>
+      </div>
+    </div>
+  </div>
+</div>
+<section>
+  {{ partial "recent-articles/main.html" . }}
+</section>