fix: add missing HOME import to models.py (NameError crash)

get_cli_sessions() and get_cli_session_messages() reference HOME but
it was not imported from api.config. This caused /api/sessions to 500
on every request, breaking the entire session list.

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

api/models.py

@@ -10,7 +10,7 @@ from pathlib import Path
 import api.config as _cfg
 from api.config import (
     SESSION_DIR, SESSION_INDEX_FILE, SESSIONS, SESSIONS_MAX,
-    LOCK, DEFAULT_WORKSPACE, DEFAULT_MODEL, PROJECTS_FILE
+    LOCK, DEFAULT_WORKSPACE, DEFAULT_MODEL, PROJECTS_FILE, HOME
 )
 from api.workspace import get_last_workspace