fix: users loop clobbered requesting username in settings filtering

The users-section loop reused 'username' as its loop variable, overwriting
the requesting user's name so host/threshold filtering compared against the
last user in the config. Rename to 'uname' and add a regression test with a
user that is not last in the users dict.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NfPpSpccTWBfZg1FTveyaU

hbd/server/settings.py

@@ -238,11 +238,11 @@ def get_settings_sections(config: dict, threshold_checker=None, user=None) -> li
 
     # ---- Users (show metadata only, never password hashes) ----------------
     users_list = []
-    for username, attrs in (config.get("users") or {}).items():
+    for uname, attrs in (config.get("users") or {}).items():
         if not isinstance(attrs, dict):
             continue
         users_list.append({
-            "username": username,
+            "username": uname,
             "full_name": attrs.get("full_name", ""),
             "admin": bool(attrs.get("admin", False)),
             "avatar": attrs.get("avatar", ""),