feat(ui): route all in-app external links through Telegram openLink

Extend the openLink routing from the dictionary lookup to every external
link shown inside the Mini App, so none triggers the WebView's 'open this
link?' confirmation. A shared onExternalLinkClick handler resolves the anchor
via closest() (so it also works delegated on {@html} content), backed by a
pure routeExternalLinkInTelegram decision: only inside Telegram, only an
external http(s) target=_blank link, excluding same-origin/in-app and t.me
links (t.me keeps openTelegramLink). Applied to the word-check lookup, the
About rules link, the Feedback operator-reply links, and the feature-gated
announcement banner.

Outside Telegram every anchor keeps its native target=_blank.

docs/UI_DESIGN.md

@@ -73,7 +73,10 @@ Login uses `Screen`.
   **closing confirmation** is enabled while a game is open **on mobile only** (on desktop
   closing is deliberate and the "changes may not be saved" dialog is just noise — move drafts
   auto-save); **vertical swipes** (swipe-to-minimise)
-  are disabled so they don't fight tile drag or the board scroll; and a live stream dropped
+  are disabled so they don't fight tile drag or the board scroll; **external links** (the word-check
+  dictionary lookup, the rules link, operator-reply links) open through `Telegram.WebApp.openLink`
+  so Telegram shows them in its in-app browser instead of the WebView's "open this link?"
+  confirmation a plain `target=_blank` triggers; and a live stream dropped
   by a background suspend reconnects silently on return — the connection banner is
   suppressed while hidden and for a short grace after resume (visibilitychange +
   pageshow/pagehide + Telegram `activated`/`deactivated`).