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

frontend/packages/dashboard/src/tabs.js

@@ -23,7 +23,6 @@ import {
   fetchAndRenderToolGroups,
   initPermissions,
 } from "./permissions.js";
-import { refreshSchedules, activeScheduleCount } from "./schedules.js";
 import {
   initJobqRollup,
   syncTransientsFromSnapshot,
@@ -56,7 +55,6 @@ window.marked = marked;
   const MANAGED_SECTION_IDS = [
     "containers-section",
     "inbox-section",
-    "schedules-section",
     "capabilities-section",
     "tool-groups-section",
   ];
@@ -149,7 +147,6 @@ window.marked = marked;
       // mount's own effect handles the actual fetch.
       initJobqRollup();
       renderContainers(s);
-      refreshSchedules();
       restoreOpenDetails(openDetails);
       // No periodic refresh timer. Phase 6 covers every container
       // mutation with `ContainerStateChanged` / `ContainerRemoved`
@@ -248,8 +245,8 @@ window.marked = marked;
   })();
 
   // ─── tab routing ───────────────────────────────────────────────────────
-  // Hash-based: `#swarm` / `#system` / `#permissions` /
-  // `#schedules` activate the matching pane on the dashboard. Empty
+  // Hash-based: `#swarm` / `#system` / `#permissions` activate the
+  // matching pane on the dashboard. Empty
   // hash defaults to SW4RM. FL0W and ST4TS are NOT tabs —
   // they're separate pages (`/flow.html`, `/stats.html`) reached from
   // the H0M3 hub. Tab routing only
@@ -266,11 +263,6 @@ window.marked = marked;
     // visibility (bar only belongs on SW4RM where agent cards live).
     document.body.dataset.activeTab = target;
     renderSelectionBar(Array.from(containersState.values()));
-    // Re-fetch on activation as a safety net: SSE covers live mutations,
-    // re-sync covers disconnect windows.
-    if (target === "schedules") {
-      refreshSchedules();
-    }
     // Permissions tables: SSE covers worker-applied changes
     // (capabilities_changed / tool_groups_changed); re-fetch on
     // activation as a safety net for any gap between SSE events and
@@ -310,9 +302,6 @@ window.marked = marked;
       if (c.needs_update) swarm++;
     }
     setTabCount("swarm", swarm);
-    // SCH3DUL3S — count of schedules with at least one still-active
-    // target: the ones left to recreate with `swarmctl schedule`.
-    setTabCount("schedules", activeScheduleCount());
   }
   // Poll the state stores on a 1s tick to keep the pill counts in
   // sync. The state stores are mutated synchronously by every SSE