Add React UI with Execution Explorer, auth, and standalone deployment

- Scaffold Vite + React + TypeScript frontend in ui/ with full design
  system (dark/light themes) matching the HTML mockups
- Implement Execution Explorer page: search filters, results table with
  expandable processor tree and exchange detail sidebar, pagination
- Add UI authentication: UiAuthController (login/refresh endpoints),
  JWT filter handles ui: subject prefix, CORS configuration
- Shared components: StatusPill, DurationBar, StatCard, AppBadge,
  FilterChip, Pagination — all using CSS Modules with design tokens
- API client layer: openapi-fetch with auth middleware, TanStack Query
  hooks for search/detail/snapshot queries, Zustand for state
- Standalone deployment: Nginx Dockerfile, K8s Deployment + ConfigMap +
  NodePort (30080), runtime config.js for API base URL
- Embedded mode: maven-resources-plugin copies ui/dist into JAR static
  resources, SPA forward controller for client-side routing
- CI/CD: UI build step, Docker build/push for server-ui image, K8s
  deploy step for UI, UI credential secrets

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/theme/ThemeProvider.tsx

@@ -0,0 +1,12 @@
+import { useEffect } from 'react';
+import { useThemeStore } from './theme-store';
+
+export function ThemeProvider({ children }: { children: React.ReactNode }) {
+  const theme = useThemeStore((s) => s.theme);
+
+  useEffect(() => {
+    document.documentElement.setAttribute('data-theme', theme);
+  }, [theme]);
+
+  return <>{children}</>;
+}