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.

assets/icons/ghost.svg

@@ -0,0 +1,2 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 384 512">
+<path fill="currentColor" d="M50.8 452.1L19.2 477.4c-2.1 1.7-4.7 2.6-7.4 2.6C5.3 480 0 474.7 0 468.2V192C0 86 86 0 192 0S384 86 384 192V468.2c0 6.5-5.3 11.8-11.8 11.8c-2.7 0-5.3-.9-7.4-2.6l-31.6-25.3c-3.3-2.7-7.5-4.1-11.8-4.1c-5.9 0-11.5 2.8-15 7.5l-37.6 50.1c-3 4-7.8 6.4-12.8 6.4s-9.8-2.4-12.8-6.4l-38.4-51.2c-3-4-7.8-6.4-12.8-6.4s-9.8 2.4-12.8 6.4l-38.4 51.2c-3 4-7.8 6.4-12.8 6.4s-9.8-2.4-12.8-6.4L77.6 455.5c-3.6-4.7-9.1-7.5-15-7.5c-4.3 0-8.4 1.5-11.7 4.1zM160 192c0-17.7-14.3-32-32-32s-32 14.3-32 32s14.3 32 32 32s32-14.3 32-32zm96 32c17.7 0 32-14.3 32-32s-14.3-32-32-32s-32 14.3-32 32s14.3 32 32 32z"/></svg>