feat: add Logs tab with cursor-paginated search, level filters, and live tail

- Extend GET /api/v1/logs with cursor pagination, multi-level filtering,
  optional application scoping, and level count aggregation
- Add exchangeId, instanceId, application, mdc fields to log responses
- Refactor ClickHouseLogStore with keyset pagination (N+1 pattern)
- Add LogSearchRequest/LogSearchResponse core domain records
- Create LogSearchPageResponse wrapper DTO
- Add Logs as 4th content tab (Exchanges | Dashboard | Runtime | Logs)
- Implement LogSearch component with debounced search, level filter bar,
  expandable log entries, cursor pagination, and live tail mode
- Add cross-navigation: exchange header → logs, log tab → logs tab
- Update ClickHouseLogStoreIT with cursor, multi-level, cross-app tests

Closes: #104

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/router.tsx

@@ -16,6 +16,7 @@ const OidcConfigPage = lazy(() => import('./pages/Admin/OidcConfigPage'));
 const DatabaseAdminPage = lazy(() => import('./pages/Admin/DatabaseAdminPage'));
 const ClickHouseAdminPage = lazy(() => import('./pages/Admin/ClickHouseAdminPage'));
 const AppConfigPage = lazy(() => import('./pages/Admin/AppConfigPage'));
+const LogsPage = lazy(() => import('./pages/LogsTab/LogsPage'));
 const SwaggerPage = lazy(() => import('./pages/Swagger/SwaggerPage'));
 
 function SuspenseWrapper({ children }: { children: React.ReactNode }) {
@@ -68,6 +69,11 @@ export const router = createBrowserRouter([
           { path: 'runtime/:appId', element: <SuspenseWrapper><RuntimePage /></SuspenseWrapper> },
           { path: 'runtime/:appId/:instanceId', element: <SuspenseWrapper><RuntimePage /></SuspenseWrapper> },
 
+          // Logs tab
+          { path: 'logs', element: <SuspenseWrapper><LogsPage /></SuspenseWrapper> },
+          { path: 'logs/:appId', element: <SuspenseWrapper><LogsPage /></SuspenseWrapper> },
+          { path: 'logs/:appId/:routeId', element: <SuspenseWrapper><LogsPage /></SuspenseWrapper> },
+
           // Legacy redirects — Sidebar uses hardcoded /apps/... and /agents/... paths
           { path: 'apps', element: <Navigate to="/exchanges" replace /> },
           { path: 'apps/:appId', element: <LegacyAppRedirect /> },