Add official hackathon track tag to README

Added mcp-in-action-track-productivity tag for MCP-1st-Birthday hackathon submission.

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

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

README.md

@@ -17,6 +17,8 @@ tags:
   - dbt
   - airflow
   - etl
+  - mcp-in-action-track-productivity
+  - hackathon
 ---
 
 # Lineage Graph Accelerator 🔥