feat(ui): one-tap confirm deeplink screen + client language

Add the /confirm/<token> SPA route and Confirm screen: a prefetch-safe button
POSTs the token via a new confirmEmailLink RPC (client/transport/mock/codec +
ConfirmLinkResult model). A login adopts the minted session and enters the app; a
link shows confirmed / merge-in-the-app; an invalid or expired token asks for a new
code. Exempt /confirm from the no-session /login redirect. Forward the client
locale on the email request (authEmailRequest gains language → app.locale) so a
fresh web login email is localised. Handle the new 'profile' live-event sub-kind by
re-fetching the profile, so a link confirmed in another browser reflects in-app at
once. i18n en+ru.

ui/src/lib/codec.test.ts

@@ -117,7 +117,7 @@ describe('codec', () => {
     expect(guest.browserTz()).toBe('-05:30');
 
     const email = fb.EmailRequestRequest.getRootAsEmailRequestRequest(
-      new ByteBuffer(encodeEmailRequest('a@example.com', '+00:00')),
+      new ByteBuffer(encodeEmailRequest('a@example.com', '+00:00', 'en')),
     );
     expect(email.email()).toBe('a@example.com');
     expect(email.browserTz()).toBe('+00:00');