Add Gitea sync service with full and incremental modes, paged API fetch, upsert logic for users/repos/commits/PRs, and error aggregation.
Add migration for git_users, git_repositories, git_commits, git_pull_requests with indexes and unique constraints; add models and sync scripts for full/incremental jobs.
Update Gitea UI and dashboard filters (user/repo/date), aggregate commit loading across repositories, and wire routes/controllers/sidebar for dashboard and sync endpoints.
