fix: handle empty commenter name in mention notification emails (#400)

Use `||` instead of `??` so empty strings also fall back to email.
The nullish coalescing operator (`??`) only catches null/undefined,
so users with an empty name string would appear nameless in emails.

packages/api/src/utils/notifications.ts

@@ -53,7 +53,7 @@ export async function sendMentionEmails({
     const commenter = await userRepo.getById(db, commenterUserId);
     if (!commenter) return;
 
-    const commenterName = commenter.name ?? commenter.email;
+    const commenterName = commenter.name?.trim() || commenter.email;
 
     // Get mentioned members with full details (filtered by workspace)
     const membersWithDetails = await memberRepo.getByPublicIdsWithUsers(