issue-4114: Fix unassigned sample referral lookup

[soumajitgh]

Summary

Fixes the invalid referral property and mapped-association joins used when finding an unassigned sample by accession number.

Changes

• Filter referrals with valid ReferralStatus values, excluding canonical CANCELLED and legacy CANCELED states.
• Traverse the mapped Referral, Analysis, SampleItem, and Sample associations so Hibernate generates valid SQL.
• Add database-backed regression coverage for eligible, cancelled, assigned, and nonexistent samples.

Verification

• mvn test -Dtest=SampleDAOImplTest: 4 passed
• mvn spotless:check: passed

Issue

Fixes #4114
#4114