bug: checkDuplicateDevice uses random IV encryption (cannot detect duplicates)

Summary

\ in \ uses \ which generates a random IV for each encryption. This means the same serial number produces different ciphertext each time, making duplicate detection impossible.

Current Behavior

\
Same serial number produces different ciphertext → duplicate never found.

Expected Behavior

Should use \ for fields that need duplicate detection:

\

Files Affected

Related

• Discovered during test coverage improvement for Issue #790
• Test file:

Priority

Medium - Feature doesn't work as intended but has workaround (manual verification)