Implement PWA (Progressive Web App) Support for KLiK POS

[maniamartial]

Add PWA support to Klik POS to enable offline use, installability, and native-like features.

Problem Statement

• No offline support; POS fails without internet

• Not installable on devices

• No background sync for failed transactions

Proposed Solution

Implement PWA features:

• Service Worker for offline caching and background sync

• Web App Manifest for installability

• Push notifications for alerts and updates(Might be trickier than we think)

• Offline-first architecture for core POS functions

Features to Implement

Phase 1: Core PWA Setup

• Service Worker registration and basic caching

• Web App Manifest configuration

• Install prompts and app-like experience

• Basic offline functionality

Phase 2: Offline Support

• Cache product catalog and customer data - current we catching product for 5 minutes. With this we will have to cache for 24 hour or so.

• Offline draft invoice creation

• Background sync for pending transactions - this will only be applicable for B2C for those people using zatca, as B2B requires instant sending of invoice to zatca.

• Graceful offline indicators - green indicator and red indicator

Phase 3: Advanced Features

• Push notifications for:

• Low stock alerts

• System updates - just incase its important

• Advanced caching strategies

• Performance optimizations