fix: remove incorrect package-level yarn.lock file

- Remove packages/indexer-agent/yarn.lock (incorrect for monorepo)
- Maintain single root yarn.lock as per Yarn workspaces best practices
- Dataloader dependency correctly defined in packages/indexer-common/package.json
- Docker build confirms proper dependency resolution

Resolves CI formatting check failures caused by workspace lockfile issues.

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

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

Author: DaMandal0rian