feat(web): Tailwind 4 + shadcn/ui + ESLint

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

web/vite.config.ts

@@ -1,9 +1,16 @@
 /// <reference types="vitest/config" />
-import { defineConfig } from "vite";
+import tailwindcss from "@tailwindcss/vite";
 import react from "@vitejs/plugin-react";
+import path from "node:path";
+import { defineConfig } from "vite";
 
 export default defineConfig({
-  plugins: [react()],
+  plugins: [react(), tailwindcss()],
+  resolve: {
+    alias: {
+      "@": path.resolve(__dirname, "./src"),
+    },
+  },
   server: {
     proxy: {
       "/api": "http://localhost:8080",