Fix ADIF location and program reference fields

[rsuzuki0]

Summary

• convert existing decimal-degree mylat and mylon values to the ADIF Location representation required by MY_LAT and MY_LON
• emit dedicated MY_POTA_REF/POTA_REF and MY_WWFF_REF/WWFF_REF fields while retaining the existing generic SIG fields for compatibility
• update the declared ADIF version from 3.1.0 to 3.1.7
• document and test the corrected output

Scope

This PR does not add or change any FLE input directive. It only corrects and enriches ADIF output from data FLEcli already parses.

Validation

• go test ./...
• go test -race -count=1 ./...
• go vet ./...