fix: search endpoint crashing on User.username reference

User.username doesn't exist - usernames are in Profile model.
Now properly searches Profile.username and joins results.

backend/routers/search.py

@@ -47,13 +47,29 @@ def global_search(
         .limit(limit)
     ).all()
     
-    # Search Users (by username or email)
+    # Search Users (by email or profile username)
     users = session.exec(
         select(User)
-        .where((col(User.email).ilike(q_str)) | (col(User.username).ilike(q_str)))
+        .where(col(User.email).ilike(q_str))
         .limit(limit)
     ).all()
     
+    # Also search Profiles for username matches
+    from models import Profile
+    profile_matches = session.exec(
+        select(Profile)
+        .where(col(Profile.username).ilike(q_str))
+        .limit(limit)
+    ).all()
+    # Add unique users from profile matches
+    existing_user_ids = {u.id for u in users}
+    for p in profile_matches:
+        if p.user_id not in existing_user_ids:
+            user = session.get(User, p.user_id)
+            if user:
+                users.append(user)
+                existing_user_ids.add(user.id)
+    
     # Search Nicknames
     nicknames = session.exec(
         select(PerformanceNickname)