feat: chart-led Security overview with sortable Images and History tables (#1364)

* feat: chart-led Security overview with sortable Images and History tables

Refine the Security page around the existing design system and add the
data the dashboard needs.

- Overview leads with four charts (30-day risk trend, severity donut, top
  exposed images, findings by type); the signal-rail counts become a
  secondary summary, and the scanner and deploy-enforcement posture follow.
- Images becomes a recessed table with search, a severity filter, sortable
  columns, a last-scan column, and inline scan actions; the findings cell is
  clickable into the scan sheet, and the per-row cursor tooltip is dropped
  where the columns already carry that information.
- Policies puts deploy-enforcement first, collapses the policy packs into an
  accordion, and uses the standard primary button for Add policy.
- Suppressions and acknowledgements move their titles and Add buttons outside
  the cards, matching the Fleet tab layout.
- History switches from the detail sheet to an inline table (search, sortable
  columns, two-scan compare, pagination); the now-unreachable scan-history
  overlay is removed.
- Add GET /api/security/overview/trend, a node-scoped daily critical/high
  rollup backing the risk-trend chart.
- Extract the shared image-scan hook and the severity classifier, and harden
  the overview data fetch so a malformed non-critical response can never read
  as a clean security state.

* fix: treat malformed Security responses as errors, not empty or clean states

Address an independent review of the data-fetch paths so a 200 with an
unexpected shape can never read as a benign "no findings" view.

- SecurityView: validate that the image-summaries body is a scan-summary map; an
  unexpected shape now sets the error state instead of an empty map. Isolate the
  trend fetch in its own self-catching promise so a transport failure on the
  non-critical chart can no longer poison the overview or summaries error state.
- useImageScan: only a "completed" poll counts as success (a malformed or unknown
  status now throws), and a failed post-scan summaries refresh is logged instead
  of silently dropped.
- HistoryTab: a 200 whose body lacks an items array is treated as an error, not
  an empty "no completed scans" list.

frontend/src/components/EditorLayout/hooks/useViewNavigationState.ts

@@ -61,7 +61,6 @@ export function useViewNavigationState(options?: UseViewNavigationStateOptions)
   const [activeView, setActiveView] = useState<ActiveView>('dashboard');
   const [settingsSection, setSettingsSection] = useState<SectionId>('appearance');
   const [securityTab, setSecurityTab] = useState<SecurityTab>('overview');
-  const [securityHistoryOpen, setSecurityHistoryOpen] = useState(false);
   const [filterNodeId, setFilterNodeId] = useState<number | null>(null);
   const [schedulePrefill, setSchedulePrefill] = useState<ScheduleTaskPrefill | null>(null);
   const [mobileNavOpen, setMobileNavOpen] = useState(false);
@@ -89,11 +88,6 @@ export function useViewNavigationState(options?: UseViewNavigationStateOptions)
     const handler = (e: Event) => {
       const detail = (e as CustomEvent<SenchoNavigateDetail & { view: string }>).detail;
       if (!detail?.view) return;
-      if (detail.view === 'security-history') {
-        setSecurityHistoryOpen(true);
-        setFilterNodeId(detail.nodeId ?? null);
-        return;
-      }
       if (detail.view === 'security') {
         // Set the target tab before switching the view so the controlled
         // SecurityView lands on it deterministically (no mount race).
@@ -152,7 +146,6 @@ export function useViewNavigationState(options?: UseViewNavigationStateOptions)
     activeView, setActiveView,
     settingsSection, setSettingsSection,
     securityTab, setSecurityTab,
-    securityHistoryOpen, setSecurityHistoryOpen,
     filterNodeId, setFilterNodeId,
     schedulePrefill, setSchedulePrefill,
     mobileNavOpen, setMobileNavOpen,