Cross-device sync, per-policy time-window scheduling, and an approaching-limit countdown overlay with a one-click 1-minute extension.

Adds optional cross-device policy sync via email sign-in, plus polish on the policy view (per-domain time stats, history chart with axes and tooltips).

Curb v0.2.0 introduces policies — a single bundle of domains plus stacked daily caps and leaky-bucket rate limits, replacing the old per-site limit setup. Also adds JSON export/import, a redesigned popup that surfaces per-policy progress for the current tab, and a labeled history chart with hover tooltips.

New features: stack multiple limits per site (daily cap plus a new rate limit), a dedicated edit page with per-site history, and a few polish touches to the popup and block screen.