Offline Data + Sync

Two parallel implementations of the same problem — persisting data offline and syncing it once the connection returns — using IndexedDB and OPFS with wa-sqlite (real SQLite compiled to WebAssembly, running inside a Web Worker via asynchronous message passing). The queue of pending notes is resolved by the Service Worker's Background Sync API as soon as connectivity returns, even with the tab closed; the OPFS worker reconciles its own state once it receives the sync-completed notice. The Storage API exposes the real storage quota and protects data from cache eviction once persistence is granted.