feat(firmware-upload): add data model, APJ reader and bootloader codec

[iacker]

Description

First step of #2017, steps 1 and 2 of the implementation sequence. Adds data_model_firmware_upload.py with the APJ reader, the board and flash compatibility rules, the upload state machine, and the bootloader packet codec. Constants and image padding follow ArduPilot Tools/scripts/uploader.py. No serial, MAVLink or Tkinter code in this PR.

AI assistance was used. I reviewed the changes and ran the tests below.

Checklist

• Run pre-commit checks locally
• Verified by a human programmer
• All commits are signed off (use git commit --signoff)
• Code follows our coding standards
• Documentation updated if needed
• No breaking changes or properly documented

Testing

• Unit tests pass, 36 tests in tests/test_data_model_firmware_upload.py, including a full erase, program and CRC verify round trip against a fake rev 5 bootloader
• Integration tests pass
• Manual testing performed
• Tested on flight controller hardware

[coveralls]

Coverage Report for CI Build 33909389085

Coverage at 89.404% (no base build to compare)

Details

• Coverage remained the same as the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	19234
Covered Lines:	17196
Line Coverage:	89.4%
Relevant Branches:	5746
Covered Branches:	4745
Branch Coverage:	82.58%
Branches in Coverage %:	No
Coverage Strength:	2.66 hits per line

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💛 - Coveralls