fix(fleet-sync): make control-identity-mismatch sticky and surface in UI (#1117)

Treat 409 CONTROL_IDENTITY_MISMATCH from a replica as a non-retriable
failure instead of looping the same 409 through the 5-minute retry
service forever and silently writing identical failure rows.

Backend
- DatabaseService: add `sticky_error_code`, `sticky_error_expected`,
  `sticky_error_got` columns to `fleet_sync_status` via an idempotent
  migration. New methods setFleetSyncSticky, getFleetSyncStickyCode,
  clearFleetSyncStickyForNode. recordFleetSyncSuccess clears the sticky
  flag on a clean push. getFailedSyncTargets SQL adds
  `AND sticky_error_code IS NULL` so the retry loop skips sticky rows.
- FleetSyncService.executePushToNode: short-circuits at the top when
  sticky is set (covers event-driven pushResourceAsync calls). On a 409
  with code CONTROL_IDENTITY_MISMATCH, records the failure once and
  pins sticky with the expected/got fingerprints carried in the 409 body.
- routes/nodes.ts: new POST /api/nodes/:id/fleet-sync/reset-anchor.
  Admin + paid + node:manage. Proxies POST /api/fleet/role/reanchor to
  the peer with `{override:true}` using the stored Bearer node_proxy
  token. On peer 200, clears every sticky row for the node so the next
  push re-anchors and resumes replication. Distinct 502 / 504 responses
  for peer-rejected / peer-unreachable so the UI can show a useful toast.

Frontend
- New lib/fleetSyncApi.ts + hooks/useFleetSyncStatus.ts. Polling hook
  (30s visibilityInterval) skips fetch when !isPaid.
- NodeManager.tsx: destructive banner per affected node listing both
  fingerprints, with `Reset anchor on peer` and `Remove node` buttons.
  Hidden for community-tier users via empty hook data.
- FleetConfiguration.tsx (Fleet -> Status): read-only `Policy sync`
  SummaryRow per remote node card. In sync / degraded / paused with
  a tooltip; no action buttons (the action lives in NodeManager).

Tests
- fleet-sync-service.test.ts: 4 new cases for sticky-set on first
  mismatch, short-circuit on subsequent pushes, null fingerprints,
  and non-mismatch failures not setting sticky.
- database-fleet-sync-sticky.test.ts (new): 6 cases pinning the DB
  contract incl. retry-loop SQL filter and migration idempotency.
- nodes-fleet-sync-reset-anchor.test.ts (new): 6 cases covering
  happy path, peer 401 -> 502, peer unreachable -> 504, local-node
  rejection, unknown node id, and community-tier 403.

Gate parity (Directive 30): the new POST .../reset-anchor enforces
requireAdmin + requirePaid + node:manage (matches the existing read at
GET /api/fleet/sync-status). UI banner + SummaryRow only render when the
hook returns data, which it only does for paid-tier authed users. No
existing tier-gate file moved; this is greenfield parity.

Auth audit: the peer's POST /api/fleet/role/reanchor route already uses
requireAdmin, which accepts the central's stored node_proxy Bearer
token because authMiddleware maps `scope === 'node_proxy'` to
`req.user = { username: 'node-proxy', role: 'admin', userId: 0 }`.
No widening required.

Backend tsc clean. Frontend tsc -b clean. 59 fleet-sync tests pass; full
backend suite green minus the pre-existing Windows-only file-lock flake
on filesystem-backup.test.ts that reproduces unchanged on main.

backend/src/__tests__/fleet-sync-service.test.ts

@@ -16,6 +16,8 @@ const {
   mockInsertAuditLog,
   mockRecordFleetSyncSuccess,
   mockRecordFleetSyncFailure,
+  mockSetFleetSyncSticky,
+  mockGetFleetSyncStickyCode,
   mockGetSystemState,
   mockSetSystemState,
   mockTransaction,
@@ -33,6 +35,8 @@ const {
   mockInsertAuditLog: vi.fn(),
   mockRecordFleetSyncSuccess: vi.fn(),
   mockRecordFleetSyncFailure: vi.fn(),
+  mockSetFleetSyncSticky: vi.fn(),
+  mockGetFleetSyncStickyCode: vi.fn().mockReturnValue(null),
   mockGetSystemState: vi.fn().mockReturnValue(null),
   mockSetSystemState: vi.fn(),
   mockTransaction: vi.fn().mockImplementation((fn: () => unknown) => fn()),
@@ -53,6 +57,8 @@ vi.mock('../services/DatabaseService', () => ({
       insertAuditLog: mockInsertAuditLog,
       recordFleetSyncSuccess: mockRecordFleetSyncSuccess,
       recordFleetSyncFailure: mockRecordFleetSyncFailure,
+      setFleetSyncSticky: mockSetFleetSyncSticky,
+      getFleetSyncStickyCode: mockGetFleetSyncStickyCode,
       getSystemState: mockGetSystemState,
       setSystemState: mockSetSystemState,
       transaction: mockTransaction,
@@ -90,6 +96,7 @@ import { FleetSyncService, LOCAL_IDENTITY_SENTINEL } from '../services/FleetSync
 beforeEach(() => {
   vi.clearAllMocks();
   mockGetSystemState.mockReturnValue(null);
+  mockGetFleetSyncStickyCode.mockReturnValue(null);
 });
 
 describe('FleetSyncService.getRole', () => {
@@ -594,3 +601,102 @@ describe('FleetSyncService.formatError redaction', () => {
     expect(failure[2]).toContain('[redacted-jwt]');
   });
 });
+
+describe('FleetSyncService CONTROL_IDENTITY_MISMATCH sticky handling', () => {
+  function makeMismatchError(expected: string, got: string) {
+    return async () => {
+      const { AxiosError } = await import('axios');
+      const err = new AxiosError('Request failed with status code 409');
+      (err as unknown as { response: unknown }).response = {
+        status: 409,
+        statusText: 'Conflict',
+        data: {
+          error: `Control identity mismatch: replica is anchored to "${expected}", push from "${got}"`,
+          code: 'CONTROL_IDENTITY_MISMATCH',
+          expected,
+          got,
+        },
+      };
+      throw err;
+    };
+  }
+
+  it('sets the sticky flag carrying the expected/got fingerprints on first mismatch', async () => {
+    mockGetNodes.mockReturnValue([
+      { id: 7, type: 'remote', api_url: 'https://peer.example', api_token: 'tok', name: 'peer', mode: 'proxy' },
+    ]);
+    mockGetLocalScanPolicies.mockReturnValue([]);
+    mockGetFleetSyncStickyCode.mockReturnValue(null);
+    mockAxiosPost.mockImplementation(makeMismatchError('cb45a2eff9db81d8', '555f8d1f7e7e71e3'));
+
+    await FleetSyncService.getInstance().pushResource('scan_policies');
+
+    expect(mockRecordFleetSyncFailure).toHaveBeenCalledTimes(1);
+    expect(mockSetFleetSyncSticky).toHaveBeenCalledTimes(1);
+    expect(mockSetFleetSyncSticky).toHaveBeenCalledWith(
+      7,
+      'scan_policies',
+      'CONTROL_IDENTITY_MISMATCH',
+      'cb45a2eff9db81d8',
+      '555f8d1f7e7e71e3',
+    );
+  });
+
+  it('short-circuits subsequent pushes when sticky is already set; no HTTP call, no failure record', async () => {
+    mockGetNodes.mockReturnValue([
+      { id: 7, type: 'remote', api_url: 'https://peer.example', api_token: 'tok', name: 'peer', mode: 'proxy' },
+    ]);
+    mockGetLocalScanPolicies.mockReturnValue([]);
+    // Sticky already set from a prior push.
+    mockGetFleetSyncStickyCode.mockReturnValue('CONTROL_IDENTITY_MISMATCH');
+
+    await FleetSyncService.getInstance().pushResource('scan_policies');
+
+    expect(mockAxiosPost).not.toHaveBeenCalled();
+    expect(mockRecordFleetSyncFailure).not.toHaveBeenCalled();
+    expect(mockRecordFleetSyncSuccess).not.toHaveBeenCalled();
+    expect(mockSetFleetSyncSticky).not.toHaveBeenCalled();
+  });
+
+  it('tolerates a missing expected/got payload (passes null through)', async () => {
+    mockGetNodes.mockReturnValue([
+      { id: 7, type: 'remote', api_url: 'https://peer.example', api_token: 'tok', name: 'peer', mode: 'proxy' },
+    ]);
+    mockGetLocalScanPolicies.mockReturnValue([]);
+    mockGetFleetSyncStickyCode.mockReturnValue(null);
+    mockAxiosPost.mockImplementation(async () => {
+      const { AxiosError } = await import('axios');
+      const err = new AxiosError('Request failed with status code 409');
+      (err as unknown as { response: unknown }).response = {
+        status: 409,
+        statusText: 'Conflict',
+        data: { error: 'mismatch', code: 'CONTROL_IDENTITY_MISMATCH' },
+      };
+      throw err;
+    });
+
+    await FleetSyncService.getInstance().pushResource('scan_policies');
+
+    expect(mockSetFleetSyncSticky).toHaveBeenCalledWith(
+      7,
+      'scan_policies',
+      'CONTROL_IDENTITY_MISMATCH',
+      null,
+      null,
+    );
+  });
+
+  it('does not set sticky for non-mismatch failures (network errors, 500s)', async () => {
+    mockGetNodes.mockReturnValue([
+      { id: 7, type: 'remote', api_url: 'https://peer.example', api_token: 'tok', name: 'peer', mode: 'proxy' },
+    ]);
+    mockGetLocalScanPolicies.mockReturnValue([]);
+    mockGetFleetSyncStickyCode.mockReturnValue(null);
+    mockAxiosPost.mockRejectedValue(new Error('ECONNREFUSED'));
+
+    await FleetSyncService.getInstance().pushResource('scan_policies');
+
+    expect(mockRecordFleetSyncFailure).toHaveBeenCalledTimes(1);
+    expect(mockSetFleetSyncSticky).not.toHaveBeenCalled();
+  });
+});