chore(tooling): migrate from Biome to ESLint + Prettier

Replace Biome lint/check/format scripts with ESLint and Prettier commands, add Next + TypeScript oriented ESLint flat config, and remove biome.json. Update dependencies and lockfile to a single lint stack with Prettier-based formatting.

.prettierignore

@@ -0,0 +1,5 @@
+.next
+out
+build
+node_modules
+pnpm-lock.yaml

.prettierrc.json

@@ -0,0 +1,7 @@
+{
+  "semi": false,
+  "singleQuote": false,
+  "tabWidth": 2,
+  "printWidth": 100,
+  "trailingComma": "all"
+}

biome.json

@@ -1,67 +0,0 @@
-{
-  "$schema": "https://biomejs.dev/schemas/2.4.3/schema.json",
-  "vcs": {
-    "enabled": true,
-    "clientKind": "git",
-    "useIgnoreFile": true
-  },
-  "files": {
-    "ignoreUnknown": true,
-    "includes": [
-      "**/*.ts",
-      "**/*.tsx",
-      "**/*.js",
-      "**/*.jsx",
-      "**/*.mjs",
-      "**/*.json",
-      "**/*.css",
-      "!next-env.d.ts"
-    ]
-  },
-  "formatter": {
-    "enabled": true,
-    "indentStyle": "space",
-    "indentWidth": 2,
-    "lineWidth": 100
-  },
-  "linter": {
-    "enabled": true,
-    "rules": {
-      "recommended": true,
-      "correctness": {
-        "noUnusedImports": "error",
-        "useExhaustiveDependencies": "error"
-      },
-      "style": {
-        "noNonNullAssertion": "error",
-        "useImportType": "error"
-      },
-      "suspicious": {
-        "noExplicitAny": "error"
-      }
-    }
-  },
-  "javascript": {
-    "formatter": {
-      "quoteStyle": "double",
-      "semicolons": "asNeeded"
-    }
-  },
-  "css": {
-    "parser": {
-      "cssModules": true,
-      "tailwindDirectives": true
-    },
-    "formatter": {
-      "enabled": true
-    },
-    "linter": {
-      "enabled": true
-    }
-  },
-  "json": {
-    "formatter": {
-      "enabled": true
-    }
-  }
-}

eslint.config.mjs

@@ -0,0 +1,43 @@
+import { defineConfig, globalIgnores } from "eslint/config"
+import nextVitals from "eslint-config-next/core-web-vitals"
+import nextTypescript from "eslint-config-next/typescript"
+import prettier from "eslint-config-prettier/flat"
+
+const eslintConfig = defineConfig([
+  ...nextVitals,
+  ...nextTypescript,
+  {
+    files: ["**/*.{ts,tsx,mts,cts}"],
+    languageOptions: {
+      parserOptions: {
+        projectService: true,
+        tsconfigRootDir: import.meta.dirname,
+      },
+    },
+    rules: {
+      "react-hooks/exhaustive-deps": "error",
+      "react-hooks/set-state-in-effect": "off",
+      "react-hooks/incompatible-library": "off",
+      "@next/next/no-async-client-component": "error",
+      "@typescript-eslint/no-explicit-any": "error",
+      "@typescript-eslint/no-non-null-assertion": "error",
+      "@typescript-eslint/no-unused-vars": [
+        "warn",
+        { argsIgnorePattern: "^_", varsIgnorePattern: "^_" },
+      ],
+      "@typescript-eslint/consistent-type-imports": [
+        "error",
+        { prefer: "type-imports", fixStyle: "inline-type-imports" },
+      ],
+      "@typescript-eslint/no-floating-promises": "error",
+      "@typescript-eslint/no-misused-promises": [
+        "error",
+        { checksVoidReturn: { attributes: false } },
+      ],
+    },
+  },
+  prettier,
+  globalIgnores([".next/**", "out/**", "build/**", "node_modules/**", "next-env.d.ts"]),
+])
+
+export default eslintConfig

package.json

@@ -6,10 +6,11 @@
     "dev": "next dev --turbopack",
     "build": "next build",
     "start": "next start",
-    "lint": "biome check .",
-    "lint:fix": "biome check --write .",
-    "format": "biome format --write .",
-    "check": "biome ci .",
+    "lint": "eslint . --max-warnings=0",
+    "lint:fix": "eslint . --fix",
+    "format": "prettier \"**/*.{ts,tsx,js,jsx,mjs,cjs,json,css,yml,yaml}\" --write",
+    "format:check": "prettier \"**/*.{ts,tsx,js,jsx,mjs,cjs,json,css,yml,yaml}\" --check",
+    "check": "pnpm lint && pnpm typecheck && pnpm format:check",
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {
@@ -31,11 +32,17 @@
     "zustand": "^5.0.11"
   },
   "devDependencies": {
-    "@biomejs/biome": "^2.4.3",
     "@tailwindcss/postcss": "^4",
+    "@typescript-eslint/eslint-plugin": "^8.56.0",
+    "@typescript-eslint/parser": "^8.56.0",
     "@types/node": "^20",
     "@types/react": "^19",
     "@types/react-dom": "^19",
+    "eslint": "^9.39.3",
+    "eslint-config-next": "^16.1.6",
+    "eslint-config-prettier": "^10.1.8",
+    "eslint-plugin-react-hooks": "^7.0.1",
+    "prettier": "^3.8.1",
     "shadcn": "^3.8.5",
     "tailwindcss": "^4",
     "tw-animate-css": "^1.4.0",