Use repo src id to maintain uniqueness among repos

[ABrain7710]

Discussed Solution

1. Create alembic script that adds repo_src_id to the repo table
2. Add populate_repo_src_id task to fill repo_src_ids over time
3. Add check when inserting to make sure the repo_src_id does not exist
4. Manually clean up places where the repo_src_id is duplicated