feat: Setup React Frontend (Issue #1)

- Initialize Vite + React + TypeScript project
- Install dependencies (React Router, Zustand, Axios, Tailwind CSS)
- Configure Tailwind CSS and PostCSS
- Create basic folder structure
- Setup ESLint and Prettier
- Create placeholder pages (Login, Dashboard, Logs, Alerts, etc.)
- Create Layout and ProtectedRoute components
- Add TypeScript types

Closes #1

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -0,0 +1,37 @@
+import { BrowserRouter as Router, Routes, Route, Navigate } from 'react-router-dom'
+import Login from './pages/Login'
+import Dashboard from './pages/Dashboard'
+import LogsExplorer from './pages/LogsExplorer'
+import AlertsManager from './pages/AlertsManager'
+import PatternDetection from './pages/PatternDetection'
+import Reports from './pages/Reports'
+import Settings from './pages/Settings'
+import Layout from './components/common/Layout'
+import ProtectedRoute from './components/common/ProtectedRoute'
+
+function App() {
+  return (
+    <Router>
+      <Routes>
+        {/* Public routes */}
+        <Route path="/login" element={<Login />} />
+
+        {/* Protected routes */}
+        <Route path="/" element={<ProtectedRoute><Layout /></ProtectedRoute>}>
+          <Route index element={<Navigate to="/dashboard" replace />} />
+          <Route path="dashboard" element={<Dashboard />} />
+          <Route path="logs" element={<LogsExplorer />} />
+          <Route path="alerts" element={<AlertsManager />} />
+          <Route path="patterns" element={<PatternDetection />} />
+          <Route path="reports" element={<Reports />} />
+          <Route path="settings" element={<Settings />} />
+        </Route>
+
+        {/* 404 */}
+        <Route path="*" element={<Navigate to="/dashboard" replace />} />
+      </Routes>
+    </Router>
+  )
+}
+
+export default App