feat(phase-2): workstream 6 — Web Dashboard UI

- dashboard/: Vite 5 + React 18 + TypeScript strict SPA
  - Auth: sessionStorage credentials, TokenManager validation, AuthProvider context
  - Pages: Login, Agents (search + filter), AgentDetail (suspend/reactivate),
    Credentials (generate/rotate/revoke, new secret shown once),
    AuditLog (filters + pagination), Health (PG + Redis status, 30s refresh)
  - Components: Button, Badge, ConfirmDialog, AppShell, RequireAuth
  - All destructive actions gated by ConfirmDialog
  - Zero dangerouslySetInnerHTML; sessionStorage only (OWASP compliant)
- src/routes/health.ts: unauthenticated GET /health — PG + Redis connectivity
- src/app.ts: health route + dashboard/dist/ served at /dashboard with SPA fallback
- 6 new health route tests; 308/308 unit tests passing

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

dashboard/src/App.tsx

@@ -0,0 +1,33 @@
+import * as React from 'react';
+import { Routes, Route, Navigate } from 'react-router-dom';
+import { AuthProvider } from '@/lib/auth';
+import { RequireAuth } from '@/components/RequireAuth';
+import { AppShell } from '@/components/layout/AppShell';
+import Login from '@/pages/Login';
+import Agents from '@/pages/Agents';
+import AgentDetail from '@/pages/AgentDetail';
+import Credentials from '@/pages/Credentials';
+import AuditLog from '@/pages/AuditLog';
+import Health from '@/pages/Health';
+
+/** Top-level router — defines all application routes. */
+export default function App(): React.JSX.Element {
+  return (
+    <AuthProvider>
+      <Routes>
+        <Route path="/dashboard/login" element={<Login />} />
+        <Route element={<RequireAuth />}>
+          <Route element={<AppShell />}>
+            <Route path="/dashboard/agents" element={<Agents />} />
+            <Route path="/dashboard/agents/:agentId" element={<AgentDetail />} />
+            <Route path="/dashboard/agents/:agentId/credentials" element={<Credentials />} />
+            <Route path="/dashboard/audit" element={<AuditLog />} />
+            <Route path="/dashboard/health" element={<Health />} />
+          </Route>
+        </Route>
+        <Route path="/dashboard" element={<Navigate to="/dashboard/agents" replace />} />
+        <Route path="*" element={<Navigate to="/dashboard/agents" replace />} />
+      </Routes>
+    </AuthProvider>
+  );
+}