Fix v5 inByte/inPackets handling

[TheSynus]

NetFlow v5 was already working since the goflow2 library does support it. Testing with v5 sources I noticed that no bandwidth information was populating in ntopng.
There was a error in Handling in the formatter, byte and packet counts were read from the custom ExtendedFlowMessage fields, which are only populated for v9/IPFIX via the mapping.yaml field remapping. I just added a check if the fields are 0, in which case FlowMessage.Bytes/FlowMessage.Packets is used instead.

I have only tested this with NetFlow v5 since I don't have devices with v9 support.

[synfinatic]

@TheSynus would be great if you could sign your commit please.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.00%. Comparing base (28fee3f) to head (77eb9e0).

Files with missing lines	Patch %	Lines
formatter/ntopng_json.go	0.00%	10 Missing ⚠️
formatter/ntopng_tlv.go	0.00%	10 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #155   +/-   ##
=====================================
  Coverage   0.00%   0.00%           
=====================================
  Files          7       7           
  Lines        656     668   +12     
=====================================
- Misses       656     668   +12     

Files with missing lines	Coverage Δ
formatter/ntopng_json.go	0.00% <0.00%> (ø)
formatter/ntopng_tlv.go	0.00% <0.00%> (ø)

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[Copilot]

Pull request overview

This PR fixes missing bandwidth/accounting data for NetFlow v5 exports by falling back to FlowMessage.Bytes / FlowMessage.Packets when the custom remapped ExtendedFlowMessage IN fields are zero (which occurs when the v9/IPFIX mapping.yaml remapping is not applied).

Changes:

• Add fallback logic for in_bytes/in_packets to use baseFlow.Bytes/baseFlow.Packets when remapped fields are unpopulated.
• Apply the same fix in both ntopng output formats (TLV and JSON), with clarifying inline comments.
• Normalize OUT byte/packet values to uint64 in both formatters for consistent numeric handling.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
formatter/ntopng_tlv.go	Adds v5-safe fallback for IN bytes/packets when remapped fields are zero.
formatter/ntopng_json.go	Mirrors the same fallback logic for JSON output to keep behavior consistent across formats.

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[TheSynus]

@synfinatic I amended the commit as requested