Add DELETE /api/admin/bookings/reserve to release admin walk-in/call-in reservations.
New handler AdminCancelReservationHandler targets only RESERVATION:admin:%
entries (partitioned from user RESERVATION:user:% by WHERE clause). Includes
12 tests covering walkin + callin success, isolation, no-op, unauth, empty ctx,
walkin+callin coexistence, anon untouched, response format parity, overlapping
reservations deleted, user reservations untouched, and idempotent double-cancel.
Inverse-isolation tests in cancel_reservation_test.go prove the user-side
DELETE /api/bookings/reserve does not touch admin or anon reservations.
Add CancelReservationHandler (DELETE /api/bookings/reserve) to release authenticated user's active reservation. Register route in main.go. Add background goroutine for periodic reservation cleanup using CleanupOldReservations. Add idx_time_blockers_created_at index and extend anon cleanup to cover edit_request reservations in init-script.sql.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>