[FEATURE] Revive AxModelFitter without security bugs

[tymekaxai]

Is your feature request related to a problem? Please describe.
We should bring the AxModelFitter MCP back to production, it was deactivated in this PR: #26

Describe the solution you'd like
Our stack is ready now to bring it back to production

Would you be willing to contribute this feature?
Yes, but I would need guidance

[coderabbitai]

A summary of the changes CodeRabbit can apply:

• Create a new axiomatic_mcp/servers/axmodelfitter/server.py implementing the AxModelFitter MCP server (fit_model tool) with strict file-path validation, file-size and row-count limits, safe pandas parsing, input/bounds validation and API call logic; add axiomatic_mcp/servers/axmodelfitter/README.md documenting security changes; update pyproject.toml to register the axiomatic-axmodelfitter entry point; patch axiomatic_mcp/servers/init.py to expose axmodelfitter_mcp and register a ServerConfig for the server; and add a simple /tmp/test_import.py to verify imports—resulting in a revived, secure AxModelFitter MCP server.

• Add a new AxModelFitter MCP server package by creating axiomatic_mcp/servers/axmodelfitter/init.py (main entrypoint that runs the mcp server), main.py (module executable), and a comprehensive data_file_utils.py implementing secure file validation, format-detected pandas loaders, column-mapping validation, and functions to resolve input/output magnitudes from CSV/Excel/JSON/Parquet files to supply sanitized data to the server.

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