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>

README.md

@@ -24,6 +24,13 @@ Nail salon booking platform — Go 1.25 backend + SvelteKit 5 frontend + Docker.
 - **Today page enhancements**: interactive daily calendar grid with visual time blockers, today stats summary, responsive layout improvements
 - **Auto-select availability**: all booking flows (self-service, admin create, edit request) automatically select the first available date when data loads
 - **Shared time slot utilities**: extracted common time slot generation, lunch protection, and formatting logic into a reusable module
+- **Shared formatting utilities**: `formatDuration`, `formatDateTime`, `formatDate`, `formatTime`, `calculateAge` in `lib/utils/format.ts`
+- **Referral code registration**: new users can enter a 12-character referral code during registration; relationship recorded in `user_referrals` table
+- **Admin schedule page**: Google Calendar-style week view at `/admin/schedule` with drag-scroll, booking details modal, and working hours overlays
+- **BookingFlow welcome step**: unauthenticated users see a welcome card (Step 0) encouraging login before guest checkout, with clear messaging about lost loyalty/discount benefits
+- **Admin login redirect**: admins are redirected to `/today` after login instead of the home page
+- **Patch test duration on services**: `patch_test_duration_hours` exposed on Service type; creating a service with duration > 0 auto-creates a patch test record
+- **`created_by_name` on bookings**: admin booking details now show who created the booking (admin name)
 
 ## Project Structure
 
@@ -43,7 +50,7 @@ Crussell/
 │     ├─ admin/        # BookingCreateModal, RescheduleModal, TimeBlockers, WeeklySchedule, HolidayHours, etc.
 │     ├─ today/        # TodayCalendar (interactive grid), CurrentAppointment, PendingApprovals, TodayStats
 │     └─ account/      # EditRequestModal, UserBookingModal
-├─ frontend/src/lib/utils/  # Shared utilities (timeSlots.ts)
+├─ frontend/src/lib/utils/  # Shared utilities (timeSlots.ts, format.ts)
 ├─ sabredav/           # PHP + Composer for DAV
 ├─ nginx/              # Nginx reverse-proxy for HTTP & HTTPS
 ├─ init-scripts/       # PostgreSQL init SQL
@@ -99,7 +106,7 @@ cd backend && go build -o bin/backend ./main.go
 # Frontend
 cd frontend && npm ci && npm run build
 
-# Tests (444/447 passing, 3 skipped)
+# Tests (446/449 passing, 3 skipped)
 cd backend && go test -tags "test,dev" ./...
 ```