fix: add root Dockerfile for Glama MCP evaluation

[bch1212]

Summary

• add a repository-root Dockerfile that launches the published queryshield-mcp==1.0.1 stdio MCP server
• document that MCP directory evaluators such as Glama can use it for initialize/tool discovery without needing QUERYSHIELD_API_KEY

Why

punkpeye/awesome-mcp-servers#5852 is currently blocked on Glama quality-score evaluation. The repo already had a Dockerfile under packages/queryshield-mcp/, but Glama/awesome-mcp guidance asks for a proper Dockerfile for evaluation. This PR exposes the same slim MCP image at the repository root so directory evaluators can discover it without guessing the nested package path.

Validation

• uv run --with queryshield-mcp==1.0.1 python - <<'PY' ... imported queryshield_mcp.server and confirmed the FastMCP server name is QueryShield
• uv run --with pytest --with sqlglot --with sqlalchemy --with fastapi --with 'uvicorn[standard]' --with cryptography --with fastmcp --with httpx --with pydantic --with pydantic-settings --with python-dotenv --with python-multipart --with stripe --with sendgrid --with redis python -m pytest tests/ -q → 66 passed
• explicit diff review checks passed: root Dockerfile matches packages/queryshield-mcp/Dockerfile, uses queryshield-mcp==1.0.1, entrypoint is queryshield-mcp, README text is scope-limited, and no secret literals were added
• git diff --check → clean

Note: local Docker daemon was not running on this host, so I could not run a live docker build; the root Dockerfile is an exact copy of the existing nested MCP Dockerfile and installs the released PyPI package.