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/fire.svg

@@ -0,0 +1,2 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512">
+<path fill="currentColor"  d="M159.3 5.4c7.8-7.3 19.9-7.2 27.7 .1c27.6 25.9 53.5 53.8 77.7 84c11-14.4 23.5-30.1 37-42.9c7.9-7.4 20.1-7.4 28 .1c34.6 33 63.9 76.6 84.5 118c20.3 40.8 33.8 82.5 33.8 111.9C448 404.2 348.2 512 224 512C98.4 512 0 404.1 0 276.5c0-38.4 17.8-85.3 45.4-131.7C73.3 97.7 112.7 48.6 159.3 5.4zM225.7 416c25.3 0 47.7-7 68.8-21c42.1-29.4 53.4-88.2 28.1-134.4c-2.8-5.6-5.6-11.2-9.8-16.8l-50.6 58.8s-81.4-103.6-87.1-110.6C133.1 243.8 112 273.2 112 306.8C112 375.4 162.6 416 225.7 416z"/></svg>