feat: initial frontend - React + TypeScript + Vite

- Login page with JWT auth
- Dashboard with stats and charts
- Issues list with pagination, filtering
- Issue detail with comments, status transitions
- Create issue form
- Dark theme UI
- Docker (nginx) with API proxy to backend
- Sidebar navigation

src/components/Sidebar.tsx

@@ -0,0 +1,37 @@
+import { Link, useLocation } from 'react-router-dom'
+import type { User } from '@/types'
+
+interface Props {
+  user: User | null
+  onLogout: () => void
+}
+
+export default function Sidebar({ user, onLogout }: Props) {
+  const { pathname } = useLocation()
+  const links = [
+    { to: '/', icon: '📊', label: '仪表盘' },
+    { to: '/issues', icon: '📋', label: 'Issues' },
+    { to: '/projects', icon: '📁', label: '项目' },
+  ]
+
+  return (
+    <nav className="sidebar">
+      <div className="sidebar-header">
+        <h1>⚓ HarborForge</h1>
+      </div>
+      <ul className="nav-links">
+        {links.map((l) => (
+          <li key={l.to} className={pathname === l.to ? 'active' : ''}>
+            <Link to={l.to}>{l.icon} {l.label}</Link>
+          </li>
+        ))}
+      </ul>
+      {user && (
+        <div className="sidebar-footer">
+          <span>👤 {user.username}</span>
+          <button onClick={onLogout}>退出</button>
+        </div>
+      )}
+    </nav>
+  )
+}