Add repository badge component and docs

Introduce a new RepoBadge Vue component and accompanying docs page. The component (docs/.vitepress/theme/repo/RepoBadge.vue) renders a repository pulse card with an ECharts chart, contributor avatars, metrics (monthly stars, 90D, peak month, momentum), org rank, and responsive styling; it loads local JSON data (repo, commits_weekly, members, repo_list) and includes error/loading states and embed support. The docs page (docs/repo-badge.md) provides a generator UI to pick repos, produce embeddable iframe code, quick-repo chips, and embed-mode styling for standalone embedding.

Author: 1985312383