Refactor patch test system and add booking edit requests

- Replace patch_test_duration_hours on services with separate
  patch_tests table
- Add user_patch_tests table to track user patch test records
- Add booking edit request system: users can request time changes
- Add admin handlers to list, approve, and reject edit requests
- Add validation to prevent editing completed/cancelled bookings
- Add overlap and closed-day checks for booking edits

backend/handlers/auth/auth_test.go

@@ -291,7 +291,7 @@ func TestRegister_InvalidInput_Under16(t *testing.T) {
 	handler := http.HandlerFunc(RegisterHandler)
 
 	// Calculate a date that makes them under 16
-	under16DOB := time.Now().AddDate(-15, 0, 0).Format("2006-01-02")
+	under16DOB := time.Now().AddDate(-15, NULL, 0).Format("2006-01-02")
 
 	body := RegisterRequest{
 		FirstName:      "Young",