Nightly: refactor readability, progress callbacks, and resource handling

addon/http_session_pool.py

@@ -32,3 +32,12 @@ def get_requests_session(key: str, *, headers: Optional[dict[str, str]] = None):
             pass
     return session
 
+
+def close_all_sessions() -> None:
+    """Close and clear all pooled sessions."""
+    for session in list(_SESSIONS.values()):
+        try:
+            session.close()
+        except Exception:
+            pass
+    _SESSIONS.clear()