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/tabs.html

@@ -0,0 +1,52 @@
+{{- .Store.Set "tab-index" 0 -}}
+{{- $noop := .Inner -}}
+
+{{- $group := .Get "group" -}}
+{{- $default := .Get "default" -}}
+
+
+<div
+  class="tab__container w-full"
+  {{ with $group }}data-tab-group="{{ . }}"{{ end }}
+  {{ with $default }}data-default-tab="{{ . }}"{{ end }}>
+  <div class="tab__nav" role="tablist">
+    <div class="flex flex-wrap gap-1">
+      {{- range $nTabs, $_ := .Store.Get "tabs" -}}
+        {{- $isActive := false -}}
+        {{- if $default -}}
+          {{- $isActive = eq $default (index . "label") -}}
+        {{- else -}}
+          {{- $isActive = eq $nTabs 0 -}}
+        {{- end -}}
+        <button
+          class="tab__button px-3 py-2 text-sm font-semibold border-b-2 border-transparent rounded-t-md hover:bg-neutral-200 dark:hover:bg-neutral-700 {{ if $isActive -}}
+            tab--active
+          {{- end }}"
+          role="tab"
+          aria-selected="{{ cond $isActive `true` `false` }}"
+          data-tab-index="{{ $nTabs }}"
+          data-tab-label="{{ index . "label" }}">
+          <span class="flex items-center gap-1">
+            {{ with index . "icon" }}
+              {{ partial "icon.html" . }}
+            {{ end }}
+            {{ index . "label" }}
+          </span>
+        </button>
+      {{- end -}}
+    </div>
+  </div>
+  <div class="tab__content mt-4">
+    {{- range $nTabs, $_ := .Store.Get "tabs" -}}
+      {{- $isActive := false -}}
+      {{- if $default -}}
+        {{- $isActive = eq $default (index . "label") -}}
+      {{- else -}}
+        {{- $isActive = eq $nTabs 0 -}}
+      {{- end -}}
+      <div class="tab__panel {{ if $isActive }}tab--active{{ end }}" data-tab-index="{{ $nTabs }}">
+        {{ index . "content" | safeHTML }}
+      </div>
+    {{- end -}}
+  </div>
+</div>