Feature/phase5 sensors

[karangandhi-projects]

Summary

This PR adds real sensor backends for I2C and SPI while keeping the application code insulated via interfaces.

What changed

• Added TSL2591 light sensor backend over I2C
• Added BME280 environmental sensor backend over SPI2
• Introduced env/light abstraction layers (interfaces + types)
• Updated Docs to reflect current architecture and added flow/architecture diagrams
• CubeMX/HAL updates for I2C/SPI enablement (.ioc, generated Core files, HAL driver sources)

How to test

1. Build the project in STM32CubeIDE (Debug)
2. Flash to NUCLEO-F446RE
3. Open UART terminal (115200 8N1)
4. Run help and status
5. Verify periodic logs:
   • EnvSample prints temperature/pressure/%RH
   • LightSample prints light readings
6. Use log pause / log resume to keep CLI output readable

Notes

• This PR is structured so new sensors can be added by implementing the same interfaces without modifying the scheduler/app layer.