- **Past days:** new bookings stay blocked. Existing appointments **without** treatment can be edited/deleted; with treatment → toast `infoEditBlockedHasTreatment` (no modal). Banner clicks are not gated by `canBook` (slots still are).
- **Working hours / create:** interpret wall-clock in the **client IANA time zone** (`timeZone` on create/update, e.g. `Asia/Tehran`). Do not use Node `Date#getHours()` / `getDay()` on the server (UTC Docker vs clinic local). Helper: `zoned-civil-time.ts`.
- **Disabled feedback:** use `title` + click `toast.showInfo` with `common.readOnlyAccess` (same key as Staff/Patients) or the domain reason (`infoPastViewOnly`, `infoEditBlockedHasTreatment`).
- Prisma: `Treatment.appointmentId` is `onDelete: SetNull` — deleting an appointment does **not** cascade-delete treatments/cases/tasks; do not rely on cascade for cleanup.