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/src/ble.h

@@ -0,0 +1,26 @@
+#pragma once
+#include <stdint.h>
+
+enum ble_state_t {
+    BLE_STATE_INIT,
+    BLE_STATE_ADVERTISING,
+    BLE_STATE_CONNECTED,
+    BLE_STATE_DISCONNECTED,
+};
+
+void ble_init(void);
+void ble_tick(void);
+ble_state_t ble_get_state(void);
+const char* ble_get_device_name(void);
+const char* ble_get_mac_address(void);
+void ble_clear_bonds(void);
+bool ble_has_data(void);
+const char* ble_get_data(void);
+void ble_send_ack(void);
+void ble_send_nack(void);
+
+// BLE HID keyboard
+void ble_keyboard_press(uint8_t key, uint8_t modifier);
+void ble_keyboard_release(void);
+bool ble_is_connected(void);
+