fix(security): enforce FHIR patient compartment filtering

[SafetyMP]

Summary

• Enforce patient compartment checks for patient-scoped tokens on FHIR reads
• Require CDS Hooks patient context to match authenticated patient compartment

Test plan

• Issue patient-scoped token for patient A and verify patient B read is denied
• Verify CDS endpoint rejects cross-patient context
• Run auth policy unit tests

Closes #7

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