Add compact JSON logging option to talker_dio_logger

[Copilot]

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Provide a description of your changes below

JSON response logs were always pretty-printed across multiple console lines, which makes Flutter console output hard to copy because each line gets the platform log prefix. This change adds an opt-in compact JSON format so response payloads can be logged as a single line when needed.

• Formatter update

  • Adds prettyPrint to TalkerJsonFormatter
  • Keeps existing behavior by default (prettyPrint: true)
  • Supports compact single-line JSON with prettyPrint: false

• Dio logger integration

  • Exposes the compact JSON option through existing jsonFormatter configuration in TalkerDioLoggerSettings
  • Leaves all current logging behavior unchanged unless explicitly configured

• Docs and coverage

  • Documents the single-line JSON option in talker_dio_logger
  • Adds focused tests for compact formatter output and single-line response log generation

TalkerDioLoggerSettings(
  jsonFormatter: const TalkerJsonFormatter(prettyPrint: false),
)