feat(gateway): confirmEmailLink RPC + language on the email request + profile event

Add the confirm-link edge method (auth.email.confirm_link): a new
EmailConfirmLinkRequest/Result fbs table, the transcode const + handler + encoder,
and the backend-client call to the existing /sessions/email/confirm-link endpoint —
it rides Execute under the existing service prefix, so no proto/Caddy change. Add a
language field to EmailRequestRequest and forward it (the backend already seeds it).
Add the NotifyProfile sub-kind + notify.ProfileChanged, published by the confirm-link
handler on a successful link so an in-app session re-fetches its profile when the
email was confirmed in another browser. Regenerated fbs bindings (Go + TS).

backend/internal/notify/notify.go

@@ -69,6 +69,10 @@ const (
 	// it re-fetches profile.get to show or hide the banner. It carries no payload (the
 	// banner set rides the profile response). In-app only.
 	NotifyBanner = "banner"
+	// NotifyProfile tells the client that the viewer's own profile changed out of band
+	// (e.g. an email was confirmed via the one-tap deeplink opened in another browser),
+	// so it re-fetches profile.get. It carries no payload. In-app only.
+	NotifyProfile = "profile"
 	// NotifyUserBlocked confirms to the blocker that a per-user block took effect,
 	// carrying the blocked account, so every one of the blocker's sessions updates the
 	// in-game block/add-friend controls and the struck name in place. It is delivered