Replace USB serial/HID with Bluetooth Low Energy

Move all communication from USB to BLE. The device now advertises as
"Claude Controller" and acts as both a BLE HID keyboard (for touch
gestures) and a GATT data server (for usage updates from the daemon).

- Add NimBLE-Arduino BLE module with custom GATT service + HID keyboard
- Add third screen (Bluetooth) with connection status, MAC, reset button
- Rewrite daemon in bash using bluetoothctl/busctl for BLE GATT writes
- Add screenshot capture via LVGL snapshot over serial
- Remove TinyUSB mode — normal pio upload works again
- Update README with BLE architecture, screenshots, gesture docs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

firmware/platformio.ini

@@ -7,8 +7,14 @@ monitor_speed = 115200
 
 build_flags =
     -DARDUINO_USB_CDC_ON_BOOT=1
-    -UARDUINO_USB_MODE -DARDUINO_USB_MODE=0
+    ; HID is via BLE now, no TinyUSB needed — normal pio upload works
     -DBOARD_HAS_PSRAM
+    ; NimBLE config — peripheral-only, single connection
+    -DCONFIG_BT_NIMBLE_ROLE_BROADCASTER=1
+    -DCONFIG_BT_NIMBLE_ROLE_PERIPHERAL=1
+    -DCONFIG_BT_NIMBLE_ROLE_CENTRAL=0
+    -DCONFIG_BT_NIMBLE_ROLE_OBSERVER=0
+    -DCONFIG_BT_NIMBLE_MAX_CONNECTIONS=1
     ; LVGL config via build flags
     -DLV_CONF_SKIP
     -DLV_COLOR_DEPTH=16
@@ -29,8 +35,10 @@ build_flags =
     -DLV_USE_IMAGE=1
     -DLV_USE_ANIMIMG=0
     -DLV_TICK_CUSTOM=1
+    -DLV_USE_SNAPSHOT=1
 
 lib_deps =
     lovyan03/LovyanGFX@^1.1.16
     lvgl/lvgl@^9.2.0
     bblanchon/ArduinoJson@^7.0.0
+    h2zero/NimBLE-Arduino@^2.1.1