Implement search history tracking and saved searches to improve user experience and enable quick rebooking of favorite routes.
## Files to modify
- packages/backend/src/api/routes/search.ts
- packages/client/app/search/
- packages/client/hooks/use-flight-search.ts
- packages/client/lib/
## Out of scope
- Refactoring unrelated modules
- Changing public API contracts
- Major version bumps or breaking changes
- Performance optimizations not directly related to the issue
## Acceptance criteria
- [ ] Code changes implemented as per procedure steps
- [ ] All new code has complete type hints
- [ ] Unit tests added/updated with >90% coverage for changed code
- [ ] All tests pass: npm test
- [ ] Linting passes: npm run lint
- [ ] Type checking passes: npm run typecheck
- [ ] Documentation updated if needed
- [ ] Changes reviewed and approved
## Procedure
1. Design search history database schema
2. Implement search history API endpoints
3. Create saved searches functionality
4. Add frontend search history component
5. Implement price alerts for saved searches
6. Add search sharing via URL
7. Test search history persistence
8. Add privacy controls
Description