feat(ui): real friend-invite share with a per-bot link

The friend-code 'share' was an <a> that just opened the bot. Make it a real share:
Telegram's native share-to-chat picker inside the Mini App (openTelegramLink +
t.me/share/url), the system share sheet (navigator.share) on the web, else copy the
link. The shared deep link points at the same bot the player is in — it picks
VITE_TELEGRAM_LINK_EN/_RU by the session's service language, falling back to the
single VITE_TELEGRAM_LINK. Adds the per-bot build args across Dockerfile / compose /
ci.yaml / .env / docs; PLAN TODO-5 updated.

PLAN.md

@@ -1560,12 +1560,15 @@ cannot submit; three-way admin filter.
   unchanged). The DAWG/solver build-time agreement (the original caveat, shared with TODO-2) was
   discharged in Stage 14: the dict repo builds against the published solver + pinned
   `dafsa`/`alphabet`, byte-identical to the fixtures.
-- **TODO-5 — QR friend codes (owner's idea, Stage 8).** *Partially done in Stage 9:*
-  the deep-link scheme now exists (`f<code>`, shared Go ↔ TS), the bot redeems it on
-  launch, and the UI shows a **share-to-Telegram** link for an issued code when
-  `VITE_TELEGRAM_LINK` is configured. **Still open:** render the link as a **QR** so a
-  friend can add you by scanning rather than tapping/typing. The code semantics
-  (12 h TTL, single use, one active per issuer) stay as-is; only the delivery changes.
+- **TODO-5 — QR friend codes (owner's idea, Stage 8).** *Partially done in Stage 9, extended later:*
+  the deep-link scheme exists (`f<code>`, shared Go ↔ TS), the bot redeems it on launch, and the UI
+  offers a real **Share** control for an issued code — Telegram's native share-to-chat picker inside
+  the Mini App (`openTelegramLink` + `t.me/share/url`), the system share sheet (`navigator.share`) on
+  the web, else copy-the-link. The shared link points at the **same bot the player signed in through**:
+  it carries the session's `service_language` (now on the `Session` wire) and picks
+  `VITE_TELEGRAM_LINK_EN`/`_RU`, falling back to `VITE_TELEGRAM_LINK`. **Still open:** render the link
+  as a **QR** so a friend can add you by scanning. The code semantics (12 h TTL, single use, one active
+  per issuer) stay as-is; only the delivery changes.
 - **TODO-6 — smart default for the friend-game "game type" (owner's idea, Stage 8).**
   The play-with-friends form has no preselected variant today (an empty, required
   pick). Default it from the player's history (the variant they play most, from