chore(web): remove redundant and minimal README files

Removed 3 markdown files that provided no useful documentation:
- web/README.md: Single line "The frontend of Memos" (redundant)
- web/src/components/kit/README.md: Single line "Base components" (minimal)
- web/MARKDOWN_STYLE_GUIDE.md: Outdated styling guide (no longer applicable)

Kept comprehensive documentation files:
- web/src/components/MasonryView/README.md (implementation details)
- web/src/themes/COLOR_GUIDE.md (design system guide)
- web/src/components/ConfirmDialog/README.md (component API docs)
- web/src/store/README.md (architecture patterns)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: johnnyjoygh