M5: Patch Deployment & Job Management

Backend:
- migrations/003_jobs_scheduling.sql: retry_next_at/last_error columns,
  pg_notify trigger for immediate job dispatch, retry index
- pm-agent-client: ApplyPatchesRequest/Response, AgentJobStatus,
  RollbackResponse types; apply_patches/job_status/rollback_job
  client methods + generic POST helper
- pm-core/models: JobStatus, JobKind, PatchJob, PatchJobHost,
  CreateJobRequest, PatchJobSummary
- pm-web/routes/jobs.rs: POST/GET /api/v1/jobs, GET /jobs/:id,
  POST /jobs/:id/cancel, POST /jobs/:id/rollback
- pm-worker/job_executor.rs: NOTIFY listener, periodic scanner,
  execute_host_job, poll_running_jobs, handle_host_failure (3-retry
  exponential backoff 1m/5m/30m), sync_job_status, retry_pending_jobs
- pm-worker/main.rs: spawn job_executor

Frontend:
- types/index.ts: PatchInfo, PatchJobHost, PatchJob, PatchJobSummary,
  CreateJobRequest interfaces
- api/client.ts: jobsApi (list/get/create/cancel/rollback),
  patchesApi (getHostPatches)
- pages/PatchDeploymentPage.tsx: 3-step MUI Stepper
  (host select → configure → result)
- pages/JobsPage.tsx: job list table, expandable per-host detail,
  cancel/rollback actions with confirm dialog, load-more pagination
- App.tsx: /jobs and /deployment routes wired to real pages

cargo check: 0 errors | vite build: 0 errors

frontend/src/App.tsx

@@ -8,6 +8,9 @@ import HostsPage from './pages/HostsPage'
 import HostDetailPage from './pages/HostDetailPage'
 import GroupsPage from './pages/GroupsPage'
 import UsersPage from './pages/UsersPage'
+import DashboardPage from './pages/DashboardPage'
+import PatchDeploymentPage from './pages/PatchDeploymentPage'
+import JobsPage from './pages/JobsPage'
 
 // Placeholder pages — implemented in later milestones
 const PlaceholderPage = ({ title }: { title: string }) => (
@@ -35,15 +38,15 @@ function App() {
         <Route path="/mfa/setup" element={<RequireAuth><MfaSetupPage /></RequireAuth>} />
 
         {/* Protected — M3 */}
-        <Route path="/dashboard" element={<RequireAuth><PlaceholderPage title="Dashboard" /></RequireAuth>} />
+        <Route path="/dashboard" element={<RequireAuth><DashboardPage /></RequireAuth>} />
         <Route path="/hosts" element={<RequireAuth><HostsPage /></RequireAuth>} />
         <Route path="/hosts/:id" element={<RequireAuth><HostDetailPage /></RequireAuth>} />
         <Route path="/groups" element={<RequireAuth><GroupsPage /></RequireAuth>} />
         <Route path="/users" element={<RequireAuth><UsersPage /></RequireAuth>} />
 
         {/* Protected — later milestones */}
-        <Route path="/jobs" element={<RequireAuth><PlaceholderPage title="Jobs" /></RequireAuth>} />
-        <Route path="/deployment" element={<RequireAuth><PlaceholderPage title="Patch Deployment" /></RequireAuth>} />
+        <Route path="/jobs" element={<RequireAuth><JobsPage /></RequireAuth>} />
+        <Route path="/deployment" element={<RequireAuth><PatchDeploymentPage /></RequireAuth>} />
         <Route path="/maintenance" element={<RequireAuth><PlaceholderPage title="Maintenance Windows" /></RequireAuth>} />
         <Route path="/reports" element={<RequireAuth><PlaceholderPage title="Reports" /></RequireAuth>} />
         <Route path="/certificates" element={<RequireAuth><PlaceholderPage title="Certificates" /></RequireAuth>} />