Dashboard: one-click delete and modify icons on scheduled reservations

# Why?

**As a** user viewing my upcoming reservations on the Dashboard
**I want** one-click icons to delete or modify a reservation directly from the list
**So that** I don't have to navigate away to a separate page to cancel or change a reservation.

# What?

On the Dashboard's Scheduled/Upcoming reservations view (Phase 3/#335):
- Add a one-click **delete** icon per reservation row, calling the existing `DeleteReservation` API (confirm a web wrapper exists from Phase 3, or add one) directly from the row — likely with a lightweight confirm step (e.g. a confirm dialog or an undo toast) rather than an immediate destructive action with no confirmation.
- Add a one-click **modify** icon per reservation row, opening a small inline prompt/modal to change the reservation's details. For changing the end time specifically, this should call `ExtendReservation` (Phase 8/#340, already implemented) if that's the only field being changed; clarify during triage whether "modify" here means end-time-only (covered by `ExtendReservation`) or a fuller edit (start time, items) which would need a different/new API.

# Testing

Playwright e2e: create a reservation, delete it via the one-click icon and confirm it disappears from the dashboard; modify a reservation's end time via the one-click icon and confirm the change persists.

# Additional context

Depends on the Dashboard (#335, merged) and `ExtendReservation` (#340, merged) already existing.