Fix TypeScript build errors

frontend/.eslintrc.cjs

@@ -1,20 +1,52 @@
 module.exports = {
   root: true,
-  env: { browser: true, es2020: true },
+  env: { browser: true, es2020: true, node: true },
   extends: [
     'eslint:recommended',
     'plugin:@typescript-eslint/recommended',
     'plugin:react-hooks/recommended',
   ],
-  ignorePatterns: ['dist', '.eslintrc.cjs'],
+  ignorePatterns: ['dist', '.eslintrc.cjs', 'node_modules'],
   parser: '@typescript-eslint/parser',
+  parserOptions: {
+    ecmaVersion: 'latest',
+    sourceType: 'module',
+    ecmaFeatures: {
+      jsx: true,
+    },
+  },
   plugins: ['react-refresh'],
+  settings: {
+    react: {
+      version: 'detect',
+    },
+  },
   rules: {
     'react-refresh/only-export-components': [
       'warn',
       { allowConstantExport: true },
     ],
-    '@typescript-eslint/no-explicit-any': 'warn',
+    // TypeScript rules
+    '@typescript-eslint/no-explicit-any': 'error',
+    '@typescript-eslint/no-unused-vars': [
+      'error',
+      {
+        argsIgnorePattern: '^_',
+        varsIgnorePattern: '^_',
+      },
+    ],
+    '@typescript-eslint/explicit-function-return-type': 'off', // Too strict for React
+    '@typescript-eslint/explicit-module-boundary-types': 'off', // Too strict for React
+    // React hooks
+    'react-hooks/rules-of-hooks': 'error',
+    'react-hooks/exhaustive-deps': 'warn',
+    // General rules
+    'no-console': ['warn', { allow: ['warn', 'error'] }],
+    'no-debugger': 'error',
+    'prefer-const': 'error',
+    'no-var': 'error',
+    'object-shorthand': 'warn',
+    'prefer-arrow-callback': 'warn',
   },
 }