[FEATURE]: Add Web App Manifest (manifest.json) for PWA support

[Atharva0506]

Feature and its Use Cases

Currently, the frontend application does not include a Web App Manifest. While the app functions flawlessly in the browser, users on mobile or desktop are unable to natively "Install" the application to their home screens or launch it in a standalone display mode. Adding a manifest is a standard modern web practice to improve accessibility and user experience.

Additional Context

This change will slightly improve Lighthouse and SEO scoring.

Code of Conduct

• I have joined the Discord server and will post updates there
• I have searched existing issues to avoid duplicates