BAH-4739 | Add new dose units enum constants and fix extension path derivation logic

[sasikiran-tw]

Description:

Summary

• Added MCG and ML enum constants to the Dose domain class to support the new mcg/kg and ml/kg dosage rules
• Fixed extension path derivation logic in RulesEngineImpl to correctly resolve the rules engine execution path

Test plan

• Verify mcg/kg rule calculates dose as Dose Value × Latest Patient Weight (kg) and resolves unit to mcg
• Verify ml/kg rule calculates dose as Dose Value × Latest Patient Weight (kg) and resolves unit to ml
• Verify existing mg/kg rule is unaffected