feat: modernize development toolchain

- Add comprehensive development tooling:
  * ESLint configuration with modern JavaScript rules
  * Prettier for consistent code formatting
  * Husky for Git hooks automation
  * lint-staged for pre-commit checks
  * Conventional Commits with commitlint
  * Stylelint for CSS code quality

- Fix CSS issues:
  * Resolve duplicate selectors in layout_note.css
  * Merge duplicate selectors in layout_list.css
  * Ensure stylelint compliance

- Apply consistent code formatting:
  * Format all JavaScript, CSS, and Markdown files
  * Standardize code style across the project
  * Fix console statement warnings in main.js

- Update project documentation:
  * Enhance README with modern development practices
  * Update package.json with new scripts and dependencies

This modernization establishes a robust development environment with
automated code quality checks, consistent formatting~