🧹 [code health improvement] Refactor relationship checks to use RelationshipContext

[joy7758]

🎯 What: Refactored the _check_* functions in saee_backend/services/evidence_adequacy.py to accept a single RelationshipContext dataclass instead of five individual parameters.
💡 Why: This improves maintainability and readability by bundling the many arguments passed to the relationship checker functions into a single context object, reducing code duplication and signature length.
✅ Verification: Full test suite passes and verified structure of functions in code.
✨ Result: Cleaned up signatures for six internal functions and their dispatcher, making it easier to add new arguments to the context in the future if needed.

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PR created automatically by Jules for task 2175375804956005485 started by @joy7758

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