Disable User Submitted Geofences

[plinytheelder]

Eliminate the option to provide user submitted geofences

[hokiepokedad2]

Implemented ✅

Admins can now turn off user-submitted geofences via a new Disable Custom Geofences toggle under Admin → Settings → Features. When enabled it:

• hides both the user My Geofences page and the admin User Geofences review queue (nav items + routes),
• blocks creating, submitting, and importing custom geofences (the API returns 403),
• leaves existing geofences working — they are still served to PoracleJS so in-flight alerts do not break.

Merged in #299 (tracked in #297) and will ship in the next release. Thanks for the suggestion, @plinytheelder! 🎉