chore: replace eslint with oxlint and add lint step to CI

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: B4nan

.github/workflows/tests.yml

@@ -27,6 +27,9 @@ jobs:
       - name: Install
         run: npm ci
 
+      - name: Lint
+        run: npm run lint
+
       - name: Build
         run: npm run build
 

eslint.config.mjs

@@ -0,0 +1,8 @@
+{
+  "$schema": "https://raw.githubusercontent.com/oxc-project/oxc/main/npm/oxlint/configuration_schema.json",
+  "plugins": ["typescript", "react", "nextjs"],
+  "ignorePatterns": [".next/**", "out/**", "build/**"],
+  "rules": {
+    "no-unused-vars": "warn"
+  }
+}