Feat/ble rssi room mapper.

[MatteoCnda1]

Summary

Add a BLE RSSI room mapper example using aioble, steami_screen and
daplink_flash. Closes #412

Changes

• Added BLE/Room_Mapper/main.py: single-file example running
  on 3-4 STeaMi boards
• Mode selection via D-PAD menu (UP/DOWN + RIGHT to confirm):
  • BEACON mode: select beacon ID (M1/M2/M3), advertise continuously,
    LEFT to return to menu
  • SCANNER mode: scan all beacons, display RSSI, record measurement
    points
• Scanner features:
  • RIGHT: record current RSSI for all visible beacons as a CSV line
  • LEFT: stop and save, display summary, return to menu
  • RSSI calibration offsets per beacon to compensate hardware differences
  • CSV saved to RSSI_MAP.CSV via daplink_flash
    (point_id,beacon_name,rssi)
• Beacons placed in triangle formation recommended for best coverage
• Main loop always returns to mode selection menu after each session

Checklist

• Tested on hardware (STM32WB55 / STeaMi board)
• Beacons visible and RSSI recorded correctly
• CSV file readable after session
• Examples added (BLE/Room_Mapper/main.py)
• Commit messages follow <scope>: <Description.> format