Flutter App Update – Firebase Sync, RevenueCat Fix, UX Improvements -- 2

I have an existing Flutter mobile app (Firebase backend + RevenueCat + web scraping). Most functionality is already implemented. I need an experienced Flutter developer to update and refine several features. I believe this should not take more than a few days for an experienced developer.

Scope of Work:
1. Sync Local Storage with Firestore (Offline Support)
- Keep using local storage for offline mode
- Sync shift data with Firebase Firestore
- Handle offline → online auto sync
- Prevent duplicates (unique shift ID)
- Secure Firestore rules (user-only access)
- Ensure cross-device sync works properly

2. Fix Email Verification (Spam Issue)
- Configure Firebase Auth to use custom domain (syncmyschedule.com)
- Set up SPF, DKIM, DMARC
- Improve email template
- Ensure emails land in inbox (Gmail/Outlook)

3. RevenueCat Subscription Fix
- Verify subscription logic
- Fix free trial fetch limits
- Update UI status (trial / monthly / annual / expired)
- Test restore purchase

4. UX Improvements
- Simplify onboarding
- Improve navigation clarity
- Make main actions more intuitive

5. Minor Improvements
- Improve scraping speed (if possible)
- Update external calendar display format

Requirements:
- Strong experience with Flutter
- Firebase (Auth + Firestore)
- RevenueCat integration
- Offline-first data handling
- Clean, maintainable code

This is a simple, already-built app — not a full rebuild.

Please include:
- Similar projects you've worked on
- Estimated timeline