fix: forum user lookup handles duplicate display names

When multiple profiles share a display_name (Michael Carter, Alex
Rivera, etc.), .maybeSingle() blew up with PGRST116, returning 404.
Switched to ordered limit(1) so the earliest-created profile wins
and the route resolves deterministically.

src/app/api/forum/user-by-username/[username]/route.ts

@@ -25,6 +25,9 @@ export async function GET(
   // 1) Profile — accept EITHER username OR display_name (URL-encoded).
   //    forum_threads/forum_replies store author_name = display_name,
   //    so the link in the UI uses the display name; we resolve it here.
+  //    Multiple profiles can share a display_name (Michael Carter, Alex Rivera,
+  //    etc.) — pick the earliest-created profile deterministically rather than
+  //    erroring out with maybeSingle().
   const decoded = decodeURIComponent(username);
   let { data: profile } = await sb
     .from("forum_user_profiles")
@@ -36,8 +39,9 @@ export async function GET(
       .from("forum_user_profiles")
       .select("*")
       .eq("display_name", decoded)
-      .maybeSingle();
-    profile = r2.data;
+      .order("created_at", { ascending: true })
+      .limit(1);
+    profile = (r2.data && r2.data[0]) || null;
   }
 
   if (!profile) {