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/figure.html

@@ -0,0 +1,56 @@
+{{ $disableImageOptimization := .Site.Params.disableImageOptimization | default false }}
+{{ if .Get "default" }}
+  {{ partial "hugo-embedded/shortcodes/figure-default.html" . }}
+{{ else }}
+  {{- $url := urls.Parse (.Get "src") }}
+  {{- $altText := .Get "alt" }}
+  {{- $caption := .Get "caption" }}
+  {{- $href := .Get "href" }}
+  {{- $class := .Get "class" }}
+  {{- $figureClass := .Get "figureClass" }}
+  {{- $target := .Get "target" | default "_blank" }}
+  {{- $nozoom := .Get "nozoom" | default false -}}
+
+  <figure{{ with $figureClass }} class="{{ . }}"{{ end }}>
+  {{- with $href }}<a href="{{ . }}" {{ with $target }}target="{{ . }}"{{ end }} class="inline-block">{{ end -}}
+  {{- if findRE "^https?" $url.Scheme }}
+      <img class="my-0 rounded-md{{ with $nozoom }} nozoom{{ end }}{{ with $class }} {{ . }}{{ end }}" src="{{ $url.String }}" alt="{{ $altText }}" />
+  {{- else }}
+    {{- $resource := "" }}
+    {{- if $.Page.Resources.GetMatch ($url.String) }}
+      {{- $resource = $.Page.Resources.GetMatch ($url.String) }}
+    {{- else if resources.GetMatch ($url.String) }}
+      {{- $resource = resources.Get ($url.String) }}
+    {{- end }}
+    {{- with $resource }}
+      {{- if or $disableImageOptimization (eq .MediaType.SubType "svg")}}
+        <img
+          class="my-0 rounded-md{{ with $nozoom }} nozoom{{ end }}{{ with $class }} {{ . }}{{ end }}"
+          src="{{ .RelPermalink }}"
+          alt="{{ $altText }}"
+        />
+      {{- else }}
+        <img
+          class="my-0 rounded-md{{ with $nozoom }} nozoom{{ end }}{{ with $class }} {{ . }}{{ end }}"
+          loading="lazy"
+          decoding="async"
+          fetchpriority="auto"
+          alt="{{ $altText }}"
+          {{ with .Width }}width="{{ . }}"{{ end }}
+          {{ with .Height }}height="{{ . }}"{{ end }}
+          src="{{ (.Resize "800x").RelPermalink }}"
+          srcset="
+          {{- (.Resize "800x").RelPermalink }} 800w,
+          {{- (.Resize "1280x").RelPermalink }} 1280w"
+          sizes="(min-width: 768px) 50vw, 65vw"
+          data-zoom-src="{{ .RelPermalink }}"
+        />
+      {{- end }}
+    {{- else }}
+      <img class="my-0 rounded-md{{ with $nozoom }} nozoom{{ end }}{{ with $class }} {{ . }}{{ end }}" src="{{ $url.String }}" alt="{{ $altText }}" />
+    {{- end }}
+  {{- end }}
+  {{ if $href }}</a>{{ end }}
+  {{ with $caption }}<figcaption>{{ . | markdownify }}</figcaption>{{ end }}
+  </figure>
+{{- end -}}