Move PermissionDef out of TENANT_APPS into a new SHARED app so all
tenants read a single global definition table in public schema.
- new app apps.permission_def (label=fonrey_permission_def)
- db_table preserved as permission_defs (no rename)
- FK refs updated: fonrey_permission.PermissionDef -> fonrey_permission_def.PermissionDef
- migrations: permission_def/0001_initial creates table in public,
permission/0004 drops the now-orphan table from tenant schemas