Add dev-only env to force Freebuff limited mode

Set FREEBUFF_DEV_FORCE_LIMITED=true on localhost to make free-mode
country resolution return allowed=false, so the limited tier UX can be
exercised without a real geo block. Honored only when
NEXT_PUBLIC_CB_ENVIRONMENT === 'dev'; cache lookups are bypassed for
forced-limited requests so toggling the flag takes effect immediately.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>