Add selectable Pi 5 I2C/MIPI mode

[Daniiiil1]

Summary

• add an explicit Raspberry Pi 5 setting that switches the Navigator GPIO I2C overlay between bus 6 (external sensors) and bus 8 (MIPI camera)
• expose the setting through Commander and the Video Manager, with a reboot notice and an explicit warning about current ArduPilot behavior
• preserve the selected mode across BlueOS updates instead of silently resetting it
• parse and update only the expected GPIO 22/23 overlay inside [pi5], with backup and read-back verification

Current Navigator ArduPilot builds probe external sensors on bus 6, so this does not claim simultaneous camera and external-sensor support. The existing bus 6 sensor behavior remains the default; camera mode is opt-in.

Fixes #3984.

Validation

• 9 focused Python tests pass, including ambiguous/missing overlays, unsupported modes, CRLF preservation, comments, and unrelated sections
• Commander GET/POST/no-op flow tested with host file operations mocked; write backup and read-back verification pass
• strict mypy and ruff pass for the new backend module; isort and Black checks pass for new Python files
• ESLint and Stylelint pass for the changed frontend files
• production Vite build completes across 2,584 modules
• bash -n, ShellCheck, git diff --check, and installer mode-preservation checks pass

I do not have Pi 5 + Navigator + MIPI camera hardware available, so the final bus enumeration, camera stream, and external-sensor behavior still need hardware validation by a maintainer with that setup.

[CLAassistant]

All committers have signed the CLA.

[patrickelectric]

@joaoantoniocardoso can take a look on this ? Also, we need to do hardware validation as pointed in the PR.