docs: update all documentation for referral codes, admin schedule page, BookingFlow welcome step, format utilities, and patch_test_duration_hours
- README: add new features (referral codes, admin schedule page, welcome step, format utils, patch_test_duration_hours, created_by_name, admin login redirect), update project structure, update test count to 446/449
- Overview: add referral code support to Auth section, created_by_name to Booking System, admin schedule page to Scheduling and Admin Features, welcome step to Customer Features, update test coverage
- Technical Manual: add format.ts utilities to Shared Utilities, add /admin/schedule route, update handler descriptions (auth, bookings, services), add Referral Code System, Admin Schedule Page, BookingFlow Welcome Step, and patch_test_duration_hours sections, update test coverage
- Admin Manual: add Schedule page to main pages list, add full Schedule (Weekly Calendar View) section, add patch test duration to service creation, update referral history description
- User Manual: add referral code field to registration, add welcome step explanation to Step 1
- Future Work: update header, add #52-58 completed items, update #21 referral system status, add Phase 6 execution order
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>