feat(i18n): add Ukrainian & Chinese, fix zh/uk translation quality

Add two new languages (uk, zh / zh_CN) across the extension and website:
register them in SUPPORTED_LANGUAGES, the Chrome _locales map, the website
build/lang-init/app routing, hreflang/og/schema tags and language selectors.

Fix systematic machine-translation word-sense errors in the new zh/uk
locales (e.g. zh "Status"=地位→状态, "Leave Room"=留出空间→离开房间,
"Play"=玩→播放, "Seek"=寻找→跳转, audio Attack/Release/Knee; uk "Play"=Грати
→Відтворити, "Clear"=ЯСНО→Очистити, "Open"=ВІДЧИНЕНО→Відкрити, peers
"Однолітки"→"Учасники"), translate remaining English leftovers (Room ID,
Custom) and normalise terminology. All 15 locales pass test-locales.cjs.

Note: popup.html and website/template.html also carry the language-selector
additions here; their Ko-Fi→Support label text is part of the branding change.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

website/locales/en.json

@@ -76,7 +76,7 @@
   "COMP_FEAT_5_TELE": "Supported sites only",
   "COMP_FEAT_6_NAME": "Localization / Translation",
   "COMP_FEAT_6_DESC": "Available interface languages and translation support.",
-  "COMP_FEAT_6_KOALA": "13 Languages (and growing)",
+  "COMP_FEAT_6_KOALA": "15 Languages (and growing)",
   "COMP_FEAT_6_TELE": "English only",
   "COMP_FEAT_7_NAME": "Audio Compressor / Volume Leveling",
   "COMP_FEAT_7_DESC": "Built-in audio normalization to balance quiet dialogue and loud effects",
@@ -176,5 +176,5 @@
   "FOOTER_LEGAL_LINK": "imprint",
   "FOOTER_PRIVACY_LINK": "privacy",
   "FOOTER_DISCLAIMER": "KoalaSync is not affiliated with, endorsed by, or associated with Netflix, Disney+, Amazon, YouTube, Twitch, or any other streaming platform. All trademarks are property of their respective owners.",
-  "FOOTER_SUPPORT": "Buy me a coffee on Ko-Fi"
+  "FOOTER_SUPPORT": "Support KoalaSync"
 }