feat: add React frontend with auth, project list, import, and project detail pages

Converts packages/web from vanilla TypeScript Vite scaffold to React with:
- React 19, react-router-dom v7, @tanstack/react-query v5, Tailwind CSS v4
- JWT auth context with auto-refresh token support
- Login/Register pages, protected Layout with auth guard
- Projects list with grid cards and delete action
- ImportDialog supporting URL or file upload with API key display
- ProjectDetail with 4 tabs: Documentation, Modules, MCP Integration, Settings
- All TypeScript compiles cleanly (noEmit check passes)

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

packages/web/src/pages/Login.tsx

@@ -0,0 +1,39 @@
+import { useState } from 'react';
+import { Link, useNavigate } from 'react-router-dom';
+import { useAuth } from '../lib/auth';
+
+export default function Login() {
+  const [email, setEmail] = useState('');
+  const [password, setPassword] = useState('');
+  const [error, setError] = useState('');
+  const { login } = useAuth();
+  const navigate = useNavigate();
+
+  const handleSubmit = async (e: React.FormEvent) => {
+    e.preventDefault();
+    setError('');
+    try {
+      await login(email, password);
+      navigate('/');
+    } catch (err) {
+      setError(err instanceof Error ? err.message : 'Login failed');
+    }
+  };
+
+  return (
+    <div className="min-h-screen flex items-center justify-center bg-gray-50">
+      <div className="w-full max-w-md p-8 bg-white rounded-lg shadow">
+        <h1 className="text-2xl font-bold text-center mb-6">Sign In to Agent Fox</h1>
+        {error && <p className="text-red-500 text-sm mb-4">{error}</p>}
+        <form onSubmit={handleSubmit} className="space-y-4">
+          <input type="email" placeholder="Email" value={email} onChange={(e) => setEmail(e.target.value)} className="w-full px-3 py-2 border rounded-md" required />
+          <input type="password" placeholder="Password" value={password} onChange={(e) => setPassword(e.target.value)} className="w-full px-3 py-2 border rounded-md" required />
+          <button type="submit" className="w-full py-2 bg-blue-600 text-white rounded-md hover:bg-blue-700">Sign In</button>
+        </form>
+        <p className="text-center text-sm mt-4">
+          Don't have an account? <Link to="/register" className="text-blue-600 hover:underline">Sign Up</Link>
+        </p>
+      </div>
+    </div>
+  );
+}