Implement tasks 1-3: sidebar order, jail activation rollback, pie chart colors

Task 1: Move Configuration to last position in sidebar NAV_ITEMS

Task 2: Add automatic rollback when jail activation fails
- Back up .local override file before writing
- Restore original file (or delete) on reload failure, health-check
  failure, or jail not appearing post-reload
- Return recovered=True/False in JailActivationResponse
- Show warning/critical banner in ActivateJailDialog based on recovery
- Add _restore_local_file_sync and _rollback_activation_async helpers
- Add 3 new tests: rollback on reload failure, health-check failure,
  and double failure (recovered=False)

Task 3: Color pie chart legend labels to match their slice color
- legendFormatter now returns ReactNode with span style={{ color }}
- Import LegendPayload from recharts/types/component/DefaultLegendContent

frontend/src/layouts/MainLayout.tsx

@@ -185,9 +185,9 @@ const NAV_ITEMS: NavItem[] = [
   { label: "Dashboard", to: "/", icon: <GridRegular />, end: true },
   { label: "World Map", to: "/map", icon: <MapRegular /> },
   { label: "Jails", to: "/jails", icon: <ShieldRegular /> },
-  { label: "Configuration", to: "/config", icon: <SettingsRegular /> },
   { label: "History", to: "/history", icon: <HistoryRegular /> },
   { label: "Blocklists", to: "/blocklists", icon: <ListRegular /> },
+  { label: "Configuration", to: "/config", icon: <SettingsRegular /> },
 ];
 
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