Draft: Feature/offline save auto sync

The offline save and auto-sync feature allows volunteers to continue core actions such as patient registration, recording vitals, and assigning doctors without internet access. All actions are securely stored in the browser using IndexedDB when the application is offline. Volunteers can search and access recently saved patient data using booking numbers in offline mode. Once connectivity is restored, the system automatically synchronizes all pending offline data with the server. This ensures data reliability, continuity of care, and uninterrupted workflow in low-network environments.