feat: Add PX4 ULog format support

[zhexuany]

Issue Description

PX4 autopilot uses the ULog format for flight logging. Robocodec does not currently support reading or writing ULog files.

Background

ULog is a self-describing binary format used by PX4 and ArduPilot for logging flight data. It contains format definitions, message types, and logged data.

Proposed Solution

Add a new format module: src/io/formats/ulog/

Requirements

• Create ulog/ directory under src/io/formats/
• Implement ULog binary format parser
• Implement FormatReader trait for reading
• Implement FormatWriter trait for writing
• Implement FormatRewriter trait for conversion
• Add .ulg extension detection
• Handle ULog header and format definitions
• Parse uORB message types from ULog
• Add unit tests
• Add integration tests with sample ULog files

Acceptance Criteria

1. Can read PX4 ULog files
2. Can write PX4 ULog files
3. Can convert ULog to/from MCAP
4. Preserves all message data and timestamps

References

• PX4 ULog specification: https://docs.px4.io/main/en/dev_log/ulog_file_format
• ULog examples in PX4 source tree
• Foxglove ULog support: https://foxglove.dev/robotics/px4-ulog

Use Cases

• Flight log analysis
• Drone data pipeline integration
• Cross-format conversion for ML training

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Priority: P3 - AUV/Drone market expansion
Estimated effort: Medium