app store/gr33nhouse: install to /sd/apps or /flash/apps

The documentation has a table that mentions that apps can be put to /flash/sys/apps/, /flash/apps or /sd/apps.

The app store (gr33nhouse) currently installs to /flash/sys/apps, which seems to not match that table: https://git.flow3r.garden/flow3r/flow3r-firmware/-/blob/main/python_payload/apps/gr33nhouse/download.py#L111

This should probably be changed to either /flash/apps or /sd/apps, ideally /sd/apps as apps can then survive a full flash (which is what https://flow3r.garden/flasher does IME, perhaps worthy of another issue?), though SD may need to wait until #72 (closed) is resolved.