Two bugs:
1. save() wrote bare key "allow_proration" but ProrationService reads
   dotted "enrollment.allow_proration" — now always writes "{group}.{key}"
2. loadAllSettings() tried to read bare keys but DB had dotted keys from
   seeder — now strips group prefix on read so UI always sees bare keys

Result: toggle saves correctly, ProrationService reads the live value,
mid-month enrollment now shows prorated fee (e.g. day 16 = 15/30 × fee).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>