fix: update email display in UI after email change

The OIDC session token retains the old email after a Logto email
change. Now the server returns the new email in the response and
the frontend optimistically updates the auth cache.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/server/routes/account.ts

@@ -70,7 +70,7 @@ app.post("/email", zValidator("json", changeEmailSchema), async (c) => {
 
 	const logtoSub = await getLogtoSub(db, userId);
 	await logtoClient.updateEmail(logtoSub, newEmail);
-	return c.json({ ok: true });
+	return c.json({ ok: true, email: newEmail });
 });
 
 // ── Has Password ────────────────────────────────────────────────────