The folder guard also rejects ancestors of the home folder (/home,
C:\Users), compared in the realpath + normcase form, so a LoraManager
setting cannot widen the image server's allow-list to every user's files.
Add py/lora_manager_layout.py: the settings file in LoraManager's lookup
order (environment folder, portable plugin file, user config folder), only
the seven keys the import needs, the LoRA roots, the centralized sidecar
root, the example-images root and the active library, each folder through
one guard. Sidecar discovery for both storage modes and the local preview
and example-image lookup live there too.
The test runner and the browser test server point LoraManager's settings
lookup at a disposable folder, so no test reads the real settings.