Add Logitech Spotlight 2 Bluetooth support - #243

Summary

• recognize the Logitech Spotlight 2 Bluetooth device (046d:b506) without requiring -D
• add udev permissions for its input and hidraw interfaces
• reuse the existing Spotlight Click, Next, Back, hold-action, and pointer-motion behavior
• document the new supported device

Hardware validation

Tested with a connected Logitech Spotlight 2 over Bluetooth:

• Qt 5 build succeeds
• generated udev rules pass udevadm verify
• projecteur --device-scan finds all three interfaces as readable and writable
• HID++ protocol 4.5 negotiation succeeds
• Reset, ReprogramControlsV4, and PointerSpeed initialize successfully
• the device does not advertise the legacy BatteryStatus or PresenterControl vibration features, so those optional capabilities remain disabled
• disconnect/reconnect discovery works through the existing Bluetooth scan path