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/scroll-to-top.html

@@ -0,0 +1,21 @@
+{{ $isRTL := .Site.Params.rtl | default false }}
+{{ $coffeeIsRight := and (eq (lower site.Params.buymeacoffee.globalWidgetPosition) "right") .Site.Params.buymeacoffee.globalWidget }}
+{{ if not $coffeeIsRight }}
+  {{ $coffeeIsRight = false }}
+{{ end }}
+
+{{ $needAvoidCoffee := ne $coffeeIsRight $isRTL }}
+{{ $toTopYOffset := cond $needAvoidCoffee "bottom-24" "bottom-6" }}
+
+
+<div
+  id="scroll-to-top"
+  class="fixed {{ $toTopYOffset }} end-6 z-50 transform translate-y-4 opacity-0 duration-200">
+  <a
+    href="#the-top"
+    class="pointer-events-auto flex h-12 w-12 items-center justify-center rounded-full bg-neutral/50 text-xl text-neutral-700 hover:text-primary-600 dark:bg-neutral-800/50 dark:text-neutral dark:hover:text-primary-400"
+    aria-label="{{ i18n "nav.scroll_to_top_title" }}"
+    title="{{ i18n "nav.scroll_to_top_title" }}">
+    &uarr;
+  </a>
+</div>