fix(ui): interface language follows the device, not the Telegram bot

On login the UI no longer overrides the interface language from the account's
preferred_language. The live interface follows the device — the explicit local
choice (saved, locked) or the system-language guess — so opening the mini-app via
the ru-bot on an English system keeps the interface English (it was forced to
Russian by the account seed). preferred_language is still written from Settings and
used for out-of-app push routing; it just no longer dictates the UI on launch.

ui/src/lib/app.svelte.ts

@@ -341,7 +341,11 @@ async function adoptSession(s: Session): Promise<void> {
   await saveSession(s);
   try {
     app.profile = await gateway.profileGet();
-    if (!app.localeLocked) setLocale(localeFrom(app.profile.preferredLanguage, app.locale));
+    // The live interface language follows the device — the explicit local choice (locked, saved
+    // in prefs) or the system guess made at bootstrap — and is no longer overridden from the
+    // account here. preferred_language stays the user's saved choice (written from Settings,
+    // and used for out-of-app push routing), but the Telegram bot a user signs in through must
+    // not dictate the UI: a ru-bot launch on an English system stays English.
   } catch (err) {
     handleError(err);
   }