hive: remove the read-only schedules page and the old schedule store

Scheduled prompts live at swarm level (swarm-controller's
/api/schedules, `swarmctl schedule`, the swarm UI's /schedules page).
The hive dashboard's SCH3DUL3S tab only listed the rows left in
hive-c0re's `scheduled_prompts` table so operators could copy them
over; the operator confirmed everything is migrated.

Removed:
- the SCH3DUL3S tab, its pane, schedules.js, its CSS (including the
  `.rqe-source*` rules, whose only emitter was schedules.js) and the
  hub tile's "schedules" entry
- hive-c0re's GET /api/schedules and the `scheduled_prompts` store
  (with its v1 column migration and test)
- hive-sh4re's `schedule` wire types, which only that route used
- docs describing the tab, the route and the two tables

The rebuild-queue cancel route that shared the module moves to
dashboard/rebuild_queue.rs under an OpenAPI tag of its own.

The two sqlite tables are not dropped: nothing opens them any more,
and persistence.md says they can be dropped by hand.

Closes #4916

docs/web-ui/shape.md

@@ -208,7 +208,7 @@ re-render), call `refreshState()`. State shapes live in
 `hive-c0re/src/dashboard/state_snapshot.rs::StateSnapshot` and
 `web_ui/state.rs::StateSnapshot` — when
 adding state fields, plumb through the snapshot struct and the
-relevant domain module (`swarm.js`, `schedules.js`, etc.) render function.
+relevant domain module (`swarm.js`, `permissions.js`, etc.) render function.
 
 **Focus preservation:** `refreshState` checks whether
 `document.activeElement` sits inside one of the managed sections