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/nl.json

@@ -50,7 +50,7 @@
   "FEATURE_7_TITLE": "Volume egaliseren / Audiocompressor",
   "FEATURE_7_DESC": "Niet langer aan de volumeknop zitten. De ingebouwde audiocompressor versterkt stille dialogen en dempt harde explosies. Werkt op Netflix, Prime Video, Disney+, YouTube en elke HTML5-video. Volledig lokaal — geen audiogegevens verlaten uw computer.",
   "FEATURE_8_TITLE": "Open Source (MIT License)",
-  "FEATURE_8_DESC": "The entire codebase is publicly auditable on GitHub. No black boxes, no proprietary blobs — 100% transparency from the relay server to the browser extension.",
+  "FEATURE_8_DESC": "De volledige codebase is openbaar controleerbaar op GitHub. Geen zwarte dozen, geen propri?taire blobs - 100% transparantie van de relayserver tot de browserextensie.",
   "COMP_TITLE": "KoalaSync vs. Teleparty",
   "COMP_SUBTITLE": "Ontdek waarom open-source, reclamevrij en privacy-first de superieure manier is om samen te kijken.",
   "COMP_COL_FEATURE": "Functie",
@@ -76,7 +76,7 @@
   "COMP_FEAT_5_TELE": "Alleen ondersteunde sites",
   "COMP_FEAT_6_NAME": "Lokalisatie / Vertaling",
   "COMP_FEAT_6_DESC": "Beschikbare interfacetalen en vertaalondersteuning.",
-  "COMP_FEAT_6_KOALA": "13 talen (en groeiend)",
+  "COMP_FEAT_6_KOALA": "15 talen (en groeiend)",
   "COMP_FEAT_6_TELE": "Alleen Engels",
   "COMP_FEAT_7_NAME": "Audiocompressor / Volume Egaliseren",
   "COMP_FEAT_7_DESC": "Ingebouwde audionormalisatie om stille dialogen en luide effecten in balans te brengen",
@@ -176,5 +176,5 @@
   "FOOTER_LEGAL_LINK": "imprint",
   "FOOTER_PRIVACY_LINK": "privacy",
   "FOOTER_DISCLAIMER": "KoalaSync is niet verbonden aan, goedgekeurd door of geassocieerd met Netflix, Disney+, Amazon, YouTube, Twitch of enig ander streamingplatform. Alle handelsmerken zijn eigendom van hun respectieve eigenaren.",
-  "FOOTER_SUPPORT": "Trakteer op een koffie via Ko-Fi"
+  "FOOTER_SUPPORT": "Support KoalaSync"
 }