chore(brand): surface ccswitch.io as the sole official website

Add an "Only Official Website" header to the three READMEs, an
About panel button, and a tray menu entry — all pointing to
ccswitch.io. Consolidates brand and SEO signals on the canonical
domain across docs, GUI, and system tray.

src/i18n/locales/en.json

@@ -643,6 +643,7 @@
     "releaseNotes": "Release Notes",
     "viewReleaseNotes": "View release notes for this version",
     "viewCurrentReleaseNotes": "View current version release notes",
+    "officialWebsite": "Official Website",
     "oneClickInstall": "One-click Install",
     "oneClickInstallHint": "Install Claude Code / Codex / Gemini CLI / OpenCode",
     "localEnvCheck": "Local environment check",

src/i18n/locales/ja.json

@@ -643,6 +643,7 @@
     "releaseNotes": "リリースノート",
     "viewReleaseNotes": "このバージョンのリリースノートを見る",
     "viewCurrentReleaseNotes": "現在のバージョンのリリースノートを見る",
+    "officialWebsite": "公式サイト",
     "oneClickInstall": "ワンクリックインストール",
     "oneClickInstallHint": "Claude Code / Codex / Gemini CLI / OpenCode をインストール",
     "localEnvCheck": "ローカル環境チェック",

src/i18n/locales/zh.json

@@ -643,6 +643,7 @@
     "releaseNotes": "更新日志",
     "viewReleaseNotes": "查看该版本更新日志",
     "viewCurrentReleaseNotes": "查看当前版本更新日志",
+    "officialWebsite": "官方网站",
     "oneClickInstall": "一键安装",
     "oneClickInstallHint": "安装 Claude Code / Codex / Gemini CLI / OpenCode",
     "localEnvCheck": "本地环境检查",