Backend: Bluetooth SPP communication service

[GoodKimchi]

Implement the backend module responsible for communicating with the robotic hand using Bluetooth Classic SPP.

Responsibilities:

• Maintain Bluetooth connection
• Send command messages to the hand
• Handle reconnection on failure

[GoodKimchi]

Plan:

Set up backend service to establish Bluetooth SPP connection with the hand (ESP32)
Start with basic connection + sending raw test commands (e.g. PINCH + closure %)
Then handle reconnection + connection stability

I’ll push initial WIP code to a branch shortly so it can be reviewed early.

[GoodKimchi]

Initial WIP pushed (see latest update below for details)

[GoodKimchi]

Pushed initial Bluetooth SPP service structure here:
https://github.com/PubInv/Yeah-Hand-Web-App/tree/oscar/bluetooth-spp-service

The backend service currently simulates connection, command sending, and disconnect flow based on the defined protocol. This allows testing the communication logic without requiring the physical device.

Next step is integrating actual serial communication and validating against the hardware once available.