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/server/handlers_auth.go

@@ -9,6 +9,7 @@ import (
 	"go.uber.org/zap"
 
 	"scrabble/backend/internal/account"
+	"scrabble/backend/internal/notify"
 )
 
 // The /api/v1/internal/sessions/* endpoints are gateway-only: the gateway has
@@ -252,11 +253,14 @@ func (s *Server) handleEmailConfirmLink(c *gin.Context) {
 		c.JSON(http.StatusOK, confirmLinkResponse{Purpose: "login", Status: "confirmed", Session: &sess})
 		return
 	}
-	status := "confirmed"
 	if res.NeedsMerge {
-		status = "merge_required"
+		c.JSON(http.StatusOK, confirmLinkResponse{Purpose: "link", Status: "merge_required"})
+		return
 	}
-	c.JSON(http.StatusOK, confirmLinkResponse{Purpose: "link", Status: status})
+	// A free link attached the email; nudge the account's in-app session(s) to re-fetch
+	// the profile, so a link confirmed in another browser reflects at once.
+	s.notifier.Publish(notify.ProfileChanged(res.Account))
+	c.JSON(http.StatusOK, confirmLinkResponse{Purpose: "link", Status: "confirmed"})
 }
 
 // tokenRequest carries an opaque session token.