feat: Implement local data persistence for dashboards (Issue #14)

[NithinRegidi]

📝 PR Description:

🎯 Summary

This PR implements local data persistence for dashboards as requested in Issue #14, enabling users to save, load, and automatically restore their dashboard states locally in the browser.

🔧 Implementation Details

Core Features:

• IndexedDB Storage: Robust client-side database for storing dashboard data and configurations
• Auto-Save: Automatically saves dashboard state after successful data loading
• Background Sync: Real-time data updates with silent background fetching every 5 minutes
• Offline Support: Queue processing for offline operations with automatic sync when back online
• Manual Controls: Save, Load, and Clear buttons for explicit persistence management
• Auto-Restore: Prompts users to restore previous sessions on page load
• Status Indicators: Real-time feedback for all persistence operations

Technical Approach:

• Uses IndexedDB API for scalable client-side storage (vs localStorage)
• Implements offline-first design with sync queues
• Progressive Web App (PWA) features for enterprise-grade functionality
• Comprehensive error handling and data validation
• Mobile-responsive UI with status indicators

📁 Files Changed

• app/src/scripts/script.js - Added IndexedDB functions, persistence logic, and background sync
• app/src/scripts/load.js - Added offline detection, sync queue processing, and auto-restore
• index.html - Added persistence control buttons and status indicator
• app/src/styles/style.css - Added styling for persistence UI and status indicators

🎨 UI Changes

• Added Save (💾), Load (📂), and Clear (🗑️) buttons in the filter section
• Added status indicator showing current persistence state
• Auto-restore prompt on page load when saved data exists
• Color-coded status indicators (success/loading/offline states)

📱 Browser Compatibility

• Modern browsers with IndexedDB support (Chrome, Firefox, Edge, Safari)
• Graceful degradation for unsupported browsers

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Ready for review and testing! The implementation provides a seamless persistence experience while maintaining the app's performance and user experience. 🚀

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[github-actions]

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[github-actions]

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[NithinRegidi]

@multiverseweb Please review this PR