server/app.py defaulted to allow_origins=["*"] combined with
allow_credentials=True when cors_origins was not passed. That
combination is invalid per the CORS spec — browsers reject it — and
when used loosely it signals that any cross-origin request with
credentials is allowed, exposing session cookies and auth headers.
The reference config at configs/openjarvis/config.toml binds to
0.0.0.0 without setting cors_origins, so this fallback fired in every
default deployment.
Default to a closed list (Vite dev origin + Tauri webview) instead of
the wildcard. Users who actually need a custom origin already pass it
via cors_origins.
Closes#222
