feat(loyalty-discount): implement loyalty and discount system

- Add discount campaign management and validation logic
- Update booking handlers with discount application flow
- Add customer relationship endpoints for loyalty tracking
- Update frontend modals (booking, approval, payment, reschedule)
- Add DiscountsManagement and loyalty reference documentation
- Update dev scripts and database init for discount tables
- Clean up completed plan files

init-scripts/init-script.sql

@@ -237,8 +237,7 @@ CREATE TABLE bookings (
     created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
     updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
     created_by CHAR(12),
-    idempotency_key VARCHAR(64) UNIQUE,
-    discount_eligible BOOLEAN NOT NULL DEFAULT FALSE
+    idempotency_key VARCHAR(64) UNIQUE
 );
 
 CREATE INDEX idx_bookings_userid ON bookings(user_id);