chore(deps-dev): bump frontend-dev-tools group + migrate to ESLint flat config (#205)

devDeps:
- @types/node ^25.2.3 -> ^25.6.0
- eslint ^8.57.1 -> ^9.39.4 (NOT ^10: eslint-config-next 16 + ESLint 10
  broken upstream — eslint-plugin-react@7 not yet ESLint 10 compatible)
- eslint-config-next ^15.5.14 -> ^16.2.3
- prettier ^3.8.1 -> ^3.8.2
- typescript ^5.5.4 -> ^6.0.2

Migration:
- .eslintrc.json -> eslint.config.js (flat config required by ESLint 9+)
- add global.d.ts for CSS module side-effect imports (TS 6 stricter)
- relax 'no-console' for scripts/

Co-authored-by: Yaroslav Vasylenko <neuron7x@users.noreply.github.com>

Author: dependabot[bot]

apps/web/.eslintrc.json

@@ -0,0 +1,50 @@
+const next = require('eslint-config-next')
+const prettierFlat = require('eslint-config-prettier/flat')
+const prettierPlugin = require('eslint-plugin-prettier')
+const tseslint = require('@typescript-eslint/eslint-plugin')
+
+module.exports = [
+  ...next,
+  prettierFlat,
+  {
+    files: ['**/*.ts', '**/*.tsx'],
+    plugins: { prettier: prettierPlugin, '@typescript-eslint': tseslint },
+    rules: {
+      'prettier/prettier': 'error',
+      '@typescript-eslint/no-unused-vars': [
+        'error',
+        { argsIgnorePattern: '^_', varsIgnorePattern: '^_' },
+      ],
+      '@typescript-eslint/no-explicit-any': 'warn',
+      '@typescript-eslint/explicit-function-return-type': 'off',
+      '@typescript-eslint/explicit-module-boundary-types': 'off',
+      'react/react-in-jsx-scope': 'off',
+      'no-console': ['warn', { allow: ['warn', 'error'] }],
+    },
+  },
+  {
+    files: ['**/*.js', '**/*.cjs', '**/*.mjs'],
+    plugins: { prettier: prettierPlugin },
+    rules: {
+      'prettier/prettier': 'error',
+    },
+  },
+  {
+    files: ['scripts/**'],
+    rules: {
+      'no-console': 'off',
+    },
+  },
+  {
+    ignores: [
+      '.next/**',
+      'next-env.d.ts',
+      'out/**',
+      'build/**',
+      'dist/**',
+      'playwright-report/**',
+      'test-results/**',
+      'coverage/**',
+    ],
+  },
+]

apps/web/eslint.config.js

@@ -0,0 +1 @@
+declare module '*.css'