fix(web): restructure client as standalone Vite project

- client/ now has its own package.json (independent Vite project)
- Tailwind + PostCSS config inlined into vite.config.ts
- dev:client uses `cd client && npm run dev` (CWD = Vite root)
- Root package.json only has server deps
- Fix tsconfig deprecation (remove baseUrl)
- Add `npm run setup` for one-command install

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/client/vite.config.ts

@@ -1,15 +1,64 @@
 import { defineConfig } from 'vite';
 import react from '@vitejs/plugin-react';
 import path from 'path';
+import tailwindcss from 'tailwindcss';
+import autoprefixer from 'autoprefixer';
 
 export default defineConfig({
   plugins: [react()],
-  root: path.resolve(__dirname),
   resolve: {
     alias: {
       '@': path.resolve(__dirname, 'src'),
     },
   },
+  css: {
+    postcss: {
+      plugins: [
+        tailwindcss({
+          content: ['./index.html', './src/**/*.{ts,tsx}'],
+          darkMode: 'class',
+          theme: {
+            extend: {
+              colors: {
+                border: 'hsl(240 3.7% 15.9%)',
+                input: 'hsl(240 3.7% 15.9%)',
+                ring: 'hsl(240 4.9% 83.9%)',
+                background: 'hsl(240 10% 3.9%)',
+                foreground: 'hsl(0 0% 98%)',
+                primary: {
+                  DEFAULT: 'hsl(0 0% 98%)',
+                  foreground: 'hsl(240 5.9% 10%)',
+                },
+                secondary: {
+                  DEFAULT: 'hsl(240 3.7% 15.9%)',
+                  foreground: 'hsl(0 0% 98%)',
+                },
+                muted: {
+                  DEFAULT: 'hsl(240 3.7% 15.9%)',
+                  foreground: 'hsl(240 5% 64.9%)',
+                },
+                accent: {
+                  DEFAULT: 'hsl(240 3.7% 15.9%)',
+                  foreground: 'hsl(0 0% 98%)',
+                },
+                destructive: {
+                  DEFAULT: 'hsl(0 62.8% 30.6%)',
+                  foreground: 'hsl(0 0% 98%)',
+                },
+              },
+              borderRadius: {
+                lg: '0.5rem',
+                md: 'calc(0.5rem - 2px)',
+                sm: 'calc(0.5rem - 4px)',
+              },
+            },
+          },
+          plugins: [],
+        }),
+        autoprefixer(),
+      ],
+    },
+  },
   server: {
     port: 5173,
     proxy: {