Add AX Score client module with typed models

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Problem Statement

The Python SDK needs AX Score API support for the new AX Score Platform.

Proposed Solution

• Add AX client module mirroring JS SDK surface
• Add Pydantic models for AX types
• Add examples for batch scanning, report polling, llms.txt workflow
• Bump version

Checklist

• AXResource and AsyncAXResource classes
• AXReportsResource and AsyncAXReportsResource classes
• Pydantic models for all AX types
• Examples (batch scan, report polling, llms.txt workflow)
• README AX API section
• Version bump