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>

screenshot.sh

@@ -0,0 +1,66 @@
+#!/bin/bash
+# Take a screenshot from the SC01 Plus display via LVGL snapshot.
+# Usage: ./screenshot.sh [output.png] [port]
+
+OUTPUT="${1:-screenshot.png}"
+PORT="${2:-/dev/ttyACM0}"
+
+TMPRAW=$(mktemp /tmp/screenshot_XXXXXX.raw)
+trap "rm -f '$TMPRAW'" EXIT
+
+echo "Taking screenshot from $PORT..."
+
+python3 - "$PORT" "$TMPRAW" << 'PYEOF'
+import serial, sys
+
+port_path, raw_path = sys.argv[1], sys.argv[2]
+
+port = serial.Serial(port_path, 115200, timeout=10)
+port.reset_input_buffer()
+port.write(b"screenshot\n")
+port.flush()
+
+while True:
+    line = port.readline().decode("utf-8", errors="replace").strip()
+    if line.startswith("SCREENSHOT_START"):
+        parts = line.split()
+        w, h, raw_size = int(parts[1]), int(parts[2]), int(parts[3])
+        break
+    if line == "SCREENSHOT_ERR":
+        print("Device reported screenshot error", file=sys.stderr)
+        sys.exit(1)
+
+data = b""
+while len(data) < raw_size:
+    chunk = port.read(min(4096, raw_size - len(data)))
+    if not chunk:
+        print(f"Timeout: got {len(data)} of {raw_size} bytes", file=sys.stderr)
+        sys.exit(1)
+    data += chunk
+
+with open(raw_path, "wb") as f:
+    f.write(data)
+
+for _ in range(10):
+    line = port.readline().decode("utf-8", errors="replace").strip()
+    if line == "SCREENSHOT_END":
+        break
+
+port.close()
+print(f"Captured {w}x{h} ({len(data)} bytes)")
+PYEOF
+
+if [ $? -ne 0 ]; then
+    echo "Screenshot capture failed"
+    exit 1
+fi
+
+ffmpeg -y -f rawvideo -pixel_format rgb565le -video_size 480x320 \
+    -i "$TMPRAW" -update 1 -frames:v 1 "$OUTPUT" 2>/dev/null || true
+
+if [ -f "$OUTPUT" ]; then
+    echo "Saved: $OUTPUT"
+else
+    echo "Error: conversion failed"
+    exit 1
+fi