fix: add kycFileId > 0 filter to KYC stats queries

[TaprootFreak]

Summary

• Add kycFileId > 0 filter to countByDateRange() and getMaxKycFileIdByDateRange() in user-data.service.ts
• Without this filter, records without a KYC file (e.g. merged or inactive user_data entries with kycFileId = NULL) were included in the KYC file yearly statistics
• This makes the stats queries consistent with getUserDatasWithKycFile(), which already filters on kycFileId > 0

Affected

• GET /support/kycFileStats endpoint (compliance KYC stats page)
• 4 phantom records (user_data IDs: 5083, 1671, 6536, 8354) were incorrectly counted as closures

Test plan

• Verify KYC stats page shows correct counts after deployment
• Compare stats with Excel audit export to confirm consistency