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.

i18n/ja.yaml

@@ -0,0 +1,104 @@
+global:
+  language: "JA"
+
+article:
+  anchor_label: "アンカー"
+  date: "{{ .Date }}"
+  date_updated: "更新日: {{ .Date }}"
+  draft: "下書き"
+  edit_title: "編集"
+  reading_time:
+    one: "{{ .Count }} 分"
+    other: "{{ .Count }} 分"
+  reading_time_title: "読むのに必要な時間"
+  table_of_contents: "目次"
+  word_count:
+    one: "{{ .Count }} 文字"
+    other: "{{ .Count }} 文字"
+  views:
+    one: "{{ .Count }} ビュー"
+    other: "{{ .Count }} ビュー"
+  likes:
+    one: "{{ .Count }} いいね"
+    other: "{{ .Count }} いいね"
+  part_of_series: "この記事は連載の一部です"
+  part: "パート"
+  this_article: "この記事"
+  related_articles: "関連記事"
+  reply_by_email: "メールで返信"
+  reply_to: "{{ .Title }} への返信"
+  zen_mode_title:
+    enable: "Zenモードを有効にする"
+    disable: "Zenモードを無効にする"
+
+a11y:
+  title: "アクセシビリティ設定"
+  disable_blur: "ぼかしを無効にする"
+  disable_images: "背景画像を無効にする"
+  show_link_underline: "リンクの下線を表示する"
+  font_size: "フォントサイズ"
+
+author:
+  byline_title: "著者"
+
+code:
+  copy: "コピー"
+  copied: "コピーしました"
+
+error:
+  404_title: "ページが見つかりませんでした。 :confused:"
+  404_error: "404エラー"
+  404_description: "ご要望のページは存在しないようです。"
+
+footer:
+  dark_appearance: "ダークモードへ切り替え"
+  light_appearance: "ライトモードへ切り替え"
+  powered_by: "{{ .Hugo }} & {{ .Theme }} で構築されています"
+
+list:
+  externalurl_title: "外部サイトへリンク"
+  no_articles: "ここに掲載する記事はまだありません。"
+
+nav:
+  scroll_to_top_title: "TOPへスクロール"
+  skip_to_main: "メインコンテンツへスキップ"
+
+search:
+  open_button_title: "検索 (/)"
+  close_button_title: "閉じる (Esc)"
+  input_placeholder: "検索"
+
+sharing:
+  email: " Eメールを送る"
+  facebook: "Facebookでシェアする"
+  line: "LINEでシェアする"
+  linkedin: "LinkedInでシェアする"
+  pinterest: "Pinterestでピンする"
+  reddit: "Redditに投稿する"
+  twitter: "Twitterに投稿する"
+  bluesky: "Blueskyに投稿する"
+  whatsapp: "WhatsAppでシェアする"
+  telegram: "Telegramでシェアする"
+
+shortcode:
+  recent_articles: "最近の記事"
+
+recent:
+  show_more: "もっと見る"
+
+admonition:
+  abstract: 概要
+  bug: バグ
+  caution: 注意
+  danger: 危険
+  example: 例
+  failure: 失敗
+  important: 重要
+  info: 情報
+  note: ノート
+  question: 質問
+  quote: 引用
+  success: 成功
+  tip: ヒント
+  todo: TODO
+  warning: 警告