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/mock/client.ts

@@ -27,6 +27,7 @@ import type {
   HintResult,
   Invitation,
   InvitationSettings,
+  ConfirmLinkResult,
   LinkResult,
   MatchResult,
   MoveResult,
@@ -149,7 +150,10 @@ export class MockGateway implements GatewayClient {
   async authGuest(): Promise<Session> {
     return { ...SESSION };
   }
-  async authEmailRequest(): Promise<void> {}
+  async authEmailRequest(_email: string, _language: string): Promise<void> {}
+  async confirmEmailLink(_token: string): Promise<ConfirmLinkResult> {
+    return { purpose: 'link', status: 'confirmed', session: null };
+  }
   async authEmailLogin(): Promise<Session> {
     return { ...SESSION, isGuest: false };
   }