Initial commit: gp-mcp server

MCP stdio server for Greenplum 6.x query plan evaluation:
- explain_sql / explain_dbt_model tools
- read-only session enforcement + statement_timeout
- dbt compile integration
- all settings via env vars (no hardcoded defaults)

.gitignore

@@ -0,0 +1,11 @@
+.env
+.venv/
+venv/
+__pycache__/
+*.pyc
+*.pyo
+*.egg-info/
+.pytest_cache/
+.mypy_cache/
+.ruff_cache/
+.DS_Store