feat: add PWA offline support and Firestore offline persistence

[Shiva210Jyoti]

Description
Adds PWA capabilities and Firestore offline persistence so users can continue viewing roadmaps and checking off skills without an active internet connection.

Type of Change
✅ New feature

Related Issue
Closes #636

What's Changed

• Configured next-pwa to generate service workers and cache static assets
• Added public/manifest.json for PWA installability
• Updated src/app/layout.tsx to link the manifest
• Enabled Firestore IndexedDB offline persistence in src/lib/firebase.ts, guarded for client-only execution
• Handled multi-tab persistence limitation gracefully (failed-precondition/unimplemented errors caught and logged, not crashing)
• Fixed unrelated Jest version mismatch (25.x vs 30.x) that was crashing the test runner before any tests could run
• Adjusted AuthContext test mock for Jest 30 compatibility

Verification
✅ npm run lint — clean
✅ npm run build — successful, service worker generated at public/sw.js
✅ npm test — 17/17 tests passing
✅ Firestore offline persistence properly scoped to client-side only
✅ Existing auth and data fetching functionality untouched

Closes #636

[Shiva210Jyoti]

@Aditya948351 PR ready for review! Implemented next-pwa for service worker caching, web app manifest for installability, and Firestore IndexedDB offline persistence (properly client-guarded). Also fixed an unrelated Jest version mismatch that was crashing the test runner.

• Lint clean
• Build successful
• 17/17 tests passing

Ready whenever you get a chance

[Shiva210Jyoti]

@Aditya948351 Fixed the formatting issue — ran Prettier on the files I touched (next.config.ts, package.json, src/app/layout.tsx, src/lib/firebase.ts, src/lib/firestore-offline.ts). Lint and build still passing. Ready for re-review

[Aditya948351]

Excellent work! The Firestore offline persistence is implemented perfectly, utilizing persistentMultipleTabManager and gracefully falling back if IndexedDB fails. Updating the test mocks to support the new offline config was also a fantastic touch. Highly appreciable! LGTM! 🚀

[Shiva210Jyoti]

@Aditya948351 Thank you so much for the kind words and quick review! Really glad the implementation worked out well. Looking forward to contributing more to DevPath-Web .

[Aditya948351]

@Aditya948351 Thank you so much for the kind words and quick review! Really glad the implementation worked out well. Looking forward to contributing more to DevPath-Web .

@Shiva210Jyoti Loved your change of Implementing this features, Excellent work! The Firestore offline persistence is implemented perfectly. Using persistentMultipleTabManager and gracefully falling back if IndexedDB fails is great enhancement.

Updating the test mocks to seamlessly support the new offline config was also a fantastic touch. I am adding the quality:exceptional label to this PR because of the high quality of this architecture work and also that app can be installed now on their Home screen this feels really great.

Keep Contributing More on this Repo!

Do star repo if not already!

[Shiva210Jyoti]

@Aditya948351 Really appreciate that, thank you! Glad the offline persistence and PWA install flow turned out solid. Will keep an eye out for more issues to pick up here .