Consolidate to single server with unified package.json

- Merge client and server dependencies into root package.json
- Remove separate client/package.json and server/package.json
- Update server/index.js to serve built client static files
- Simplify Dockerfile to single build + production stage
- Update dev scripts for unified development workflow
- SPA routing serves index.html for non-API routes

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

client/vite.config.js

@@ -154,4 +154,7 @@ export default defineConfig({
       },
     },
   },
+  build: {
+    outDir: 'dist',
+  },
 });