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/lib/auth.tsx

@@ -0,0 +1,62 @@
+import { createContext, useContext, useState, useEffect, type ReactNode } from 'react';
+import { getAccessToken, clearTokens, setTokens, apiFetch } from './api';
+
+type User = { id: string; email: string; name: string };
+
+type AuthContextType = {
+  user: User | null;
+  loading: boolean;
+  login: (email: string, password: string) => Promise<void>;
+  register: (email: string, password: string, name: string) => Promise<void>;
+  logout: () => void;
+};
+
+const AuthContext = createContext<AuthContextType | null>(null);
+
+export function AuthProvider({ children }: { children: ReactNode }) {
+  const [user, setUser] = useState<User | null>(null);
+  const [loading, setLoading] = useState(true);
+
+  useEffect(() => {
+    if (getAccessToken()) {
+      apiFetch<User>('/auth/me')
+        .then(setUser)
+        .catch(() => clearTokens())
+        .finally(() => setLoading(false));
+    } else {
+      setLoading(false);
+    }
+  }, []);
+
+  const login = async (email: string, password: string) => {
+    const data = await apiFetch<{ user: User; accessToken: string; refreshToken: string }>(
+      '/auth/login',
+      { method: 'POST', body: JSON.stringify({ email, password }) },
+    );
+    setTokens(data.accessToken, data.refreshToken);
+    setUser(data.user);
+  };
+
+  const register = async (email: string, password: string, name: string) => {
+    const data = await apiFetch<{ user: User; accessToken: string; refreshToken: string }>(
+      '/auth/register',
+      { method: 'POST', body: JSON.stringify({ email, password, name }) },
+    );
+    setTokens(data.accessToken, data.refreshToken);
+    setUser(data.user);
+  };
+
+  const logout = () => { clearTokens(); setUser(null); };
+
+  return (
+    <AuthContext.Provider value={{ user, loading, login, register, logout }}>
+      {children}
+    </AuthContext.Provider>
+  );
+}
+
+export function useAuth() {
+  const ctx = useContext(AuthContext);
+  if (!ctx) throw new Error('useAuth must be used within AuthProvider');
+  return ctx;
+}