feat: implement ship model

[drduhe]

Issue #, if available: n/a

Notes

Implements ship detection model for OSML, adding a new model alongside the existing aircraft detection model.

Changes

• New ship detection model with complete implementation (src/aws/osml/models/ship/)
• Model weights for both aircraft and ship detection added to assets
• LFS tracking configured for large model files (.pth)
• Aircraft model fix to use correct weights filename

Files Added/Modified

• src/aws/osml/models/ship/app.py - Main ship detection application
• src/aws/osml/models/ship/config.py - Ship model configuration
• src/aws/osml/models/ship/__init__.py - Package initialization
• assets/ship_model_weights.pth - Ship model weights
• assets/aircraft_model_weights.pth - Aircraft model weights
• .gitattributes - LFS tracking configuration
• src/aws/osml/models/aircraft/app.py - Fixed weights filename reference

Impact

• Adds ship detection capability to the OSML model suite
• Maintains backward compatibility with existing aircraft model
• Properly handles large model files with Git LFS

Checklist

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• Code changes are compact and well-structured to facilitate easy review
• Changes are documented in the README.md and other relevant documentation pages
• PR title and description accurately reflect the changes and are detailed enough for historical tracking
• PR contains tests that cover all new code and the code has been manual tested
• All new dependencies are declared (if any), and no unnecessary libraries are added
• Performance impacts (if any) of the changes are evaluated and documented
• Security implications of the changes (if any) are reviewed and addressed
• I have read the Contributing Guidelines and agree to follow the Code of Conduct

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