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/vite.config.ts

@@ -0,0 +1,13 @@
+import { defineConfig } from 'vite';
+import react from '@vitejs/plugin-react';
+import tailwindcss from '@tailwindcss/vite';
+
+export default defineConfig({
+  plugins: [react(), tailwindcss()],
+  server: {
+    port: 5173,
+    proxy: {
+      '/api': 'http://localhost:3000',
+    },
+  },
+});