refactor(auto-update): retire per-stack gate, drive auto-update from schedules only (#1233)

* refactor(auto-update): retire per-stack gate, drive auto-update from schedules only

The per-stack Auto-update toggle in the stack sidebar context menu wrote a
gate row to `stack_auto_update_settings`, but actual updates only ran when a
`scheduled_tasks` row with `action='update'` fired. On a fresh install the
toggle was inert: detection ran every 6h, nothing was applied.

The same context menu already exposes `Schedule task`, which opens
ScheduledOperationsView pre-filled for the stack where the user can pick
`Auto-update Stack` and any cron. Keeping the toggle alongside that flow
duplicated the same action and turned the gate table into a parallel store
of "is a covering schedule active" derivable from `scheduled_tasks` itself.

Drop the gate model entirely:
- Backend: remove the `stack_auto_update_settings` table and its four
  accessors, the three routes under /api/stacks/*/auto-update, the per-stack
  skip in /api/auto-update/execute and SchedulerService.executeUpdate's
  fleet branch, and the clearStackAutoUpdateSetting call on stack delete.
  Dashboard `autoUpdate` count derives from scheduled_tasks (action='update'
  rows pinned to the node, total/enabled split).
- Frontend: drop the Auto-update entry from the sidebar context menu and its
  optimistic toggle plumbing. Drop autoUpdateSettings state, the
  /stacks/auto-update-settings fetch, and the auto-update-settings-changed
  WebSocket branch. Slim useSidebarActivitySummary (just nextRunAt; no
  enabled/total counts). AutoUpdateReadinessView's per-card autoUpdateEnabled
  now means "a covering enabled action='update' schedule exists" (per-stack
  row or fleet row on this node, earliest next_run_at wins, per-stack row
  wins on ties), with the gate-fetch removed.
- New: scheduledTasksRouter broadcasts scope: 'scheduled-tasks' on POST,
  PUT, PATCH /toggle, and DELETE so useConfigurationStatus and
  useNextAutoUpdateRun refetch under the 250ms debounce instead of waiting
  for the 60s poll. The broadcast is wrapped so a broken subscriber socket
  cannot turn a successful mutation into a 500.
- Docs: rewrite the "Per-stack control" section of auto-update-policies.mdx
  to describe the schedule-based model; update the matching troubleshooting
  entry. The misleading fleet-update help text in ScheduledOperationsView
  is corrected to reflect that every stack on the node is covered.

Tier parity: the surviving auto-update path (Schedule task -> Auto-update
Stack / All Stacks) is gated `requirePaid + requireAdmin` backend and
`isPaid + isAdmin` frontend, matching the gate the deleted routes carried.
The pre-commit grep returns no tier-related diff outside this PR's scope.

No data migration is provided: greenfield rules apply, and the leftover
table on already-shipped instances is harmless because no code reads or
writes it after this PR.

* docs: sweep remaining references to the per-stack auto-update toggle

The previous commit retired the per-stack Auto-update gate in favor of
configuring auto-update purely through scheduled tasks. This commit
removes the now-stale mentions of that toggle across the operator docs:

- docs/features/sidebar.mdx: drop the Auto-update entry from the Inspect
  group description, the matching screenshot alt-text, and the Skipper
  Note that listed it. Schedule task now carries the cross-link to
  Auto-Update Policies.
- docs/features/stack-management.mdx: drop the Auto-update list item;
  refresh the Schedule task entry to mention the Auto-update Stack action.
- docs/features/dashboard.mdx: rename the Configuration Status row from
  "Auto-update stacks" to "Auto-update schedules" with the new value
  shape, and rewrite the troubleshooting accordion to describe the
  scheduled-tasks invalidation path.
- docs/features/scheduled-operations.mdx: rewrite the Auto-update All
  Stacks row and helper text to reflect that every stack on the node is
  covered (no per-stack opt-out from this surface anymore).
- docs/features/multi-node.mdx: rewrite the Updates column definition to
  derive the Auto/Off flag from enabled Auto-update Stack / Auto-update
  All Stacks schedules instead of the removed per-stack policy.

The auto-update-policies.mdx rewrite in the previous commit already
covered the main reference page. The sidebar-context-menu.png screenshot
will be refreshed on release once the new menu is live in production;
the alt text is updated in this commit so it accurately describes the
shipping state.

No website edits needed: the Auto-Update Policies feature card description
("Schedule automatic image pulls and redeployments per stack on your own
cadence") and the feature matrix labels ("Auto-update stack schedule",
"Auto-update all stacks schedule") remain accurate under the new model.

* fix(stacks): drop orphaned requireAdmin import after auto-update route removal

CI's backend lint step flagged this PR's earlier deletion of the three
/api/stacks/*/auto-update routes: those handlers were the only callers of
`requireAdmin` inside routes/stacks.ts, leaving the named import on line 15
unreferenced. `requirePaid` and `effectiveTier` from the same line are still
in use elsewhere in the file and stay.

tsc --noEmit does not flag unused named imports; ESLint's no-unused-vars
does. Local backend lint reproduces and now reports 0 errors against the
existing 334-warning baseline.

frontend/src/components/sidebar/__tests__/SidebarActivityTicker.test.tsx

@@ -54,11 +54,11 @@ describe('SidebarActivityTicker', () => {
     });
   });
 
-  it('renders automation state with counts, next-run time, and routes click to open-auto-updates', () => {
+  it('renders automation state with next-run time, and routes click to open-auto-updates', () => {
     const nextRun = Math.floor(Date.now() / 1000) + 600;
-    const { onAction } = renderWith({ kind: 'automation', enabledCount: 3, totalCount: 8, nextRunAt: nextRun });
+    const { onAction } = renderWith({ kind: 'automation', nextRunAt: nextRun });
     expect(screen.getByText(/Auto-update/)).toBeInTheDocument();
-    expect(screen.getByText('3/8')).toBeInTheDocument();
+    expect(screen.getByText(/next run/)).toBeInTheDocument();
     expect(screen.getByTestId('ticker-dot')).toHaveClass('bg-warning');
     fireEvent.click(screen.getByRole('button'));
     expect(onAction).toHaveBeenCalledWith({ kind: 'open-auto-updates' });

frontend/src/components/sidebar/__tests__/useNextAutoUpdateRun.test.tsx

@@ -56,14 +56,14 @@ describe('useNextAutoUpdateRun', () => {
     expect(result.current).toBe(1_700);
   });
 
-  it('debounces rapid invalidations into a single refetch', async () => {
+  it('debounces rapid scheduled-tasks invalidations into a single refetch', async () => {
     renderHook(() => useNextAutoUpdateRun());
     expect(apiFetchMock).toHaveBeenCalledTimes(1);
 
     act(() => {
-      fireInvalidate({ action: 'auto-update-settings-changed' });
-      fireInvalidate({ action: 'auto-update-settings-changed' });
-      fireInvalidate({ action: 'auto-update-settings-changed' });
+      fireInvalidate({ scope: 'scheduled-tasks' });
+      fireInvalidate({ scope: 'scheduled-tasks' });
+      fireInvalidate({ scope: 'scheduled-tasks' });
     });
     // Debounce window not yet elapsed: still only the mount call.
     expect(apiFetchMock).toHaveBeenCalledTimes(1);
@@ -76,8 +76,8 @@ describe('useNextAutoUpdateRun', () => {
     renderHook(() => useNextAutoUpdateRun());
     apiFetchMock.mockClear();
     act(() => {
-      fireInvalidate({ action: 'something-else' });
       fireInvalidate({ scope: 'unrelated' });
+      fireInvalidate({ scope: 'stack' });
     });
     vi.advanceTimersByTime(500);
     expect(apiFetchMock).toHaveBeenCalledTimes(0);
@@ -98,7 +98,7 @@ describe('useNextAutoUpdateRun', () => {
     apiFetchMock.mockClear();
     unmount();
     await act(async () => {
-      fireInvalidate({ action: 'auto-update-settings-changed' });
+      fireInvalidate({ scope: 'scheduled-tasks' });
       vi.advanceTimersByTime(120_000);
     });
     expect(apiFetchMock).toHaveBeenCalledTimes(0);

frontend/src/components/sidebar/__tests__/useSidebarActivitySummary.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { __testing, countEnabledAutoUpdates } from '../useSidebarActivitySummary';
+import { __testing } from '../useSidebarActivitySummary';
 import type { NotificationItem } from '@/components/dashboard/types';
 import type { DeployPanelState } from '@/context/DeployFeedbackContext';
 
@@ -29,8 +29,6 @@ function inputs(overrides: Partial<Parameters<typeof deriveSummary>[0]> = {}) {
     tickerConnected: true,
     panelState: IDLE_PANEL,
     panelStartedAt: null,
-    autoUpdateEnabledCount: 0,
-    totalStackCount: 0,
     nextAutoUpdateRunAt: null,
     ...overrides,
   };
@@ -69,8 +67,6 @@ describe('useSidebarActivitySummary.deriveSummary', () => {
     const recent = notif({ id: 10, timestamp: NOW_SECS - 5 });
     const r = deriveSummary(inputs({
       notifications: [failure, recent],
-      autoUpdateEnabledCount: 1,
-      totalStackCount: 1,
       nextAutoUpdateRunAt: NOW_SECS + 3600,
     }), NOW_SECS);
     expect(r.kind).toBe('failure');
@@ -84,16 +80,12 @@ describe('useSidebarActivitySummary.deriveSummary', () => {
     expect(r.kind).not.toBe('failure');
   });
 
-  it('returns automation when auto-update is enabled and no recent event exists', () => {
+  it('returns automation when a next-run is known and no recent event exists', () => {
     const r = deriveSummary(inputs({
-      autoUpdateEnabledCount: 2,
-      totalStackCount: 4,
       nextAutoUpdateRunAt: NOW_SECS + 3600,
     }), NOW_SECS);
     expect(r.kind).toBe('automation');
     if (r.kind === 'automation') {
-      expect(r.enabledCount).toBe(2);
-      expect(r.totalCount).toBe(4);
       expect(r.nextRunAt).toBe(NOW_SECS + 3600);
     }
   });
@@ -102,18 +94,14 @@ describe('useSidebarActivitySummary.deriveSummary', () => {
     const recent = notif({ id: 7, timestamp: NOW_SECS - 5 });
     const r = deriveSummary(inputs({
       notifications: [recent],
-      autoUpdateEnabledCount: 1,
-      totalStackCount: 1,
       nextAutoUpdateRunAt: NOW_SECS + 3600,
     }), NOW_SECS);
     expect(r.kind).toBe('recent-event');
     if (r.kind === 'recent-event') expect(r.notif.id).toBe(7);
   });
 
-  it('drops automation when no next-run is known, even with auto-update settings present', () => {
+  it('drops automation when no next-run is known', () => {
     const r = deriveSummary(inputs({
-      autoUpdateEnabledCount: 1,
-      totalStackCount: 1,
       nextAutoUpdateRunAt: null,
     }), NOW_SECS);
     expect(r.kind).toBe('quiet-live');
@@ -160,25 +148,3 @@ describe('useSidebarActivitySummary.deriveSummary', () => {
     expect(r.kind).toBe('quiet-live');
   });
 });
-
-describe('countEnabledAutoUpdates', () => {
-  it('counts a stack with no explicit row as enabled (backend default-true contract)', () => {
-    expect(countEnabledAutoUpdates(['web', 'api'], {})).toBe(2);
-  });
-
-  it('respects an explicit false', () => {
-    expect(countEnabledAutoUpdates(['web', 'api', 'db'], { api: false })).toBe(2);
-  });
-
-  it('respects an explicit true', () => {
-    expect(countEnabledAutoUpdates(['web'], { web: true })).toBe(1);
-  });
-
-  it('returns 0 for an empty file list', () => {
-    expect(countEnabledAutoUpdates([], { web: true })).toBe(0);
-  });
-
-  it('ignores settings rows that do not correspond to known files', () => {
-    expect(countEnabledAutoUpdates(['web'], { ghost: false, web: true })).toBe(1);
-  });
-});