chore: Add ESLint configuration

- Add eslint.config.mjs with Next.js core-web-vitals preset
- Install @eslint/eslintrc for flat config compatibility

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

eslint.config.mjs

@@ -0,0 +1,16 @@
+import { dirname } from "path";
+import { fileURLToPath } from "url";
+import { FlatCompat } from "@eslint/eslintrc";
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+const compat = new FlatCompat({
+  baseDirectory: __dirname,
+});
+
+const eslintConfig = [
+  ...compat.extends("next/core-web-vitals"),
+];
+
+export default eslintConfig;

package-lock.json

@@ -41,6 +41,7 @@
         "zustand": "^5.0.3"
       },
       "devDependencies": {
+        "@eslint/eslintrc": "^3.3.3",
         "@types/bcryptjs": "^2.4.6",
         "@types/node": "^22.10.5",
         "@types/react": "^19.0.4",

package.json

@@ -51,6 +51,7 @@
     "zustand": "^5.0.3"
   },
   "devDependencies": {
+    "@eslint/eslintrc": "^3.3.3",
     "@types/bcryptjs": "^2.4.6",
     "@types/node": "^22.10.5",
     "@types/react": "^19.0.4",