chore: update dependencies and configuration for Vite and Vitest

- Bump versions of @vitejs/plugin-react, @vitest/coverage-istanbul, @vitest/coverage-v8, and @vitest/ui to their beta releases.
- Upgrade Vite and Vitest to their respective beta versions.
- Adjust Vite configuration to disable code splitting for improved React initialization stability.

frontend/package.json

@@ -67,11 +67,11 @@
     "@typescript-eslint/eslint-plugin": "^8.57.0",
     "@typescript-eslint/parser": "^8.57.0",
     "@typescript-eslint/utils": "^8.57.0",
-    "@vitejs/plugin-react": "^5.1.4",
-    "@vitest/coverage-istanbul": "^4.0.18",
-    "@vitest/coverage-v8": "^4.0.18",
+    "@vitejs/plugin-react": "^6.0.0-beta.0",
+    "@vitest/coverage-istanbul": "^4.1.0-beta.6",
+    "@vitest/coverage-v8": "^4.1.0-beta.6",
     "@vitest/eslint-plugin": "^1.6.10",
-    "@vitest/ui": "^4.0.18",
+    "@vitest/ui": "^4.1.0-beta.6",
     "autoprefixer": "^10.4.27",
     "eslint": "^10.0.0",
     "eslint-import-resolver-typescript": "^4.4.4",
@@ -93,8 +93,8 @@
     "tailwindcss": "^4.2.1",
     "typescript": "^6.0.1-rc",
     "typescript-eslint": "^8.57.0",
-    "vite": "^7.3.1",
-    "vitest": "^4.0.18",
+    "vite": "^8.0.0-beta.18",
+    "vitest": "^4.1.0-beta.6",
     "zod-validation-error": "^5.0.0"
   },
   "overrides": {
@@ -107,6 +107,9 @@
     },
     "eslint-plugin-promise": {
       "eslint": "^10.0.0"
+    },
+    "@vitejs/plugin-react": {
+      "vite": "8.0.0-beta.18"
     }
   }
 }

frontend/vite.config.ts

@@ -16,14 +16,13 @@ export default defineConfig({
   build: {
     outDir: 'dist',
     sourcemap: true,
-    // TEMPORARY: Disable code splitting to diagnose React initialization issue
-    // If this works, the problem is module loading order in async chunks
     chunkSizeWarningLimit: 2000,
-    rollupOptions: {
+    rolldownOptions: {
       output: {
-        // Disable code splitting - bundle everything into one file
-        manualChunks: undefined,
-        inlineDynamicImports: true
+        // Disable code splitting — single bundle for React init stability
+        // codeSplitting: false is the Rolldown-native approach
+        // (inlineDynamicImports is deprecated in Rolldown)
+        codeSplitting: false
       }
     }
   }