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.

ui/src/lib/deeplink.ts

@@ -36,13 +36,29 @@ export const invitationParam = (id: string): string => 'i' + id;
 /** friendCodeParam builds the start parameter that redeems a friend code. */
 export const friendCodeParam = (code: string): string => 'f' + code;
 
+function envVar(name: string): string | undefined {
+  return (import.meta.env as Record<string, string | undefined>)[name];
+}
+
 /**
- * shareLink wraps a deep-link start parameter in a t.me Mini App link, using the
- * VITE_TELEGRAM_LINK base (e.g. https://t.me/<bot>/<app>). It returns null when the
- * base is not configured, so callers can hide the share affordance.
+ * telegramBase returns the Mini App link base (e.g. https://t.me/<bot>/<app>) for a
+ * bot language: VITE_TELEGRAM_LINK_EN / _RU when lang is en/ru, else the
+ * language-agnostic VITE_TELEGRAM_LINK. Returns null when none is configured, so a
+ * shared link points at the same bot the player signed in through.
  */
-export function shareLink(param: string): string | null {
-  const base = import.meta.env.VITE_TELEGRAM_LINK as string | undefined;
+function telegramBase(lang: string): string | null {
+  const byLang =
+    lang === 'ru' ? envVar('VITE_TELEGRAM_LINK_RU') : lang === 'en' ? envVar('VITE_TELEGRAM_LINK_EN') : undefined;
+  return byLang || envVar('VITE_TELEGRAM_LINK') || null;
+}
+
+/**
+ * shareLink wraps a deep-link start parameter in a t.me Mini App link for the given
+ * bot language (the session's service language). Returns null when no base is
+ * configured, so callers can hide the share affordance.
+ */
+export function shareLink(param: string, lang = ''): string | null {
+  const base = telegramBase(lang);
   if (!base) return null;
   const sep = base.includes('?') ? '&' : '?';
   return `${base}${sep}startapp=${encodeURIComponent(param)}`;