Add offline trial, licence entry and Rust access enforcement #1230

Depends on #1228 and parent PR #1229. Add a 30-day local trial, independently stored licence state, accessible key entry/import/removal, and shared Rust gates for local scanning and Android control. Expiry must clean up held input and overlays without preventing licence recovery. Preserve account, pairing, settings sync, shipping identity and existing-client protocol compatibility. Update user docs and test with fake input/time/storage. This is the desktop implementation slice of #1217.