fix: duration in seconds missing fractions

[de-sh]

Closes #

Changes

Why?

Fractional part of time is missing on serialization

Trials Performed

JS payload after change:

{
  "timestamp": 1715249644559,
  "sequence": 13,
  "stream": "bms",
  "serialized_data_size": 133510,
  "compressed_data_size": 133510,
  "total_serialization_time": 0.022287279,
  "avg_serialization_time": 0.001714406,
  "total_compression_time": 0.0,
  "avg_compression_time": 0.0
}