chore: migrate to ESLint v9 flat config and update linting tools

[Copilot]

Migrates ESLint configuration from legacy .eslintrc.cjs format to v9 flat config format and updates all linting dependencies to latest versions.

Changes

ESLint Migration

• Migrated from .eslintrc.cjs to eslint.config.mjs flat config format
• Removed deprecated .eslintignore (ignores now inline in config)
• Removed --ext flag from lint scripts (auto-detected in v9)
• Added @eslint/compat + @eslint/eslintrc for legacy config compatibility
• Used fixupConfigRules() to bridge airbnb-typescript/v8 incompatibility

Package Updates

• ESLint: v8.57.1 → v9.39.1
• @typescript-eslint/*: v7.18.0 → v8.47.0
• eslint-config-prettier: v9.1.0 → v10.1.8
• eslint-plugin-react-hooks: v4.6.2 → v7.0.1
• eslint-plugin-jsdoc: v50.6.3 → v61.2.1
• eslint-plugin-storybook: v0.9.0 → v10.0.8
• prettier: v3.5.2 → v3.6.2
• Plus other minor plugin updates

Configuration Example

Before (.eslintrc.cjs):

module.exports = {
  root: true,
  parser: '@typescript-eslint/parser',
  extends: ['airbnb-typescript', 'prettier'],
  // ...
}

After (eslint.config.mjs):

import { fixupConfigRules } from '@eslint/compat';
import { FlatCompat } from '@eslint/eslintrc';
import js from '@eslint/js';

export default [
  { ignores: ['dist/**', 'build/**'] },
  js.configs.recommended,
  ...fixupConfigRules(
    compat.extends('airbnb-typescript', 'prettier')
  ),
  // ...
]

All existing rules and code style preserved. Build, type-check, and linting verified.

Original prompt

Update Eslint and prettier, migrating the config format to the new version.

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