feat(android): on-device OS notification capture (NotificationListenerService)

Add an Android backend to os_notification_listener.py so notifications on the
experimental Android-TV build drive the existing NotificationColorStripSource
LED effects (flash/pulse/sweep, per-app colors + sounds) at app-name parity
with the Windows/Linux backends.

A Kotlin NotificationListenerService forwards the posting app's display label
across the Chaquopy JNI boundary into a new push-based _AndroidBackend +
module-level push_notification() receiver; the existing color-strip pipeline,
per-app colors/filters, and history endpoint are reused unchanged.

- Python: _AndroidBackend (probed first), push_notification() receiver,
  _LinuxBackend.probe() hardened with is_linux() to exclude Android (which
  also reports platform.system() == "Linux").
- Android: LedGrabNotificationListener NLS — serial single-thread executor,
  full crash isolation around Python.getInstance(), label-only forwarding
  (never notification title/body), ongoing/group-summary/self-package noise
  filtering. Manifest service exported + gated by
  BIND_NOTIFICATION_LISTENER_SERVICE (no new uses-permission).
- UX: prompt-once notification-access + manual "Grant notification access"
  button wired into the D-pad focus chain (computed from visible controls);
  en/ru/zh strings.
- Tests: 11 isolated unit tests — module-global + tmp_path history isolation,
  push routing contract, callback-exception swallowing, None app-name, and a
  desktop-regression lock on backend selection order.
- Docs: README OS-support Android column (notification + audio cells),
  ANDROID-REVIEW status flipped to Implemented.

Zero new Python deps; no build.gradle.kts / Chaquopy pip changes.

README.md

@@ -105,16 +105,17 @@ LedGrab runs as a desktop / server application:
 
 ### Feature support by OS
 
-| Feature | Windows | Linux / macOS |
-| ------- | ------- | ------------- |
-| Screen capture | DXCam, BetterCam, WGC, MSS | MSS |
-| Webcam capture | OpenCV (DirectShow) | OpenCV (V4L2) |
-| Audio capture | WASAPI, Sounddevice | Sounddevice (PulseAudio/PipeWire) |
-| GPU monitoring | NVIDIA (nvidia-ml-py) | NVIDIA (nvidia-ml-py) |
-| Capture from Android phone | scrcpy (ADB) | scrcpy (ADB) |
-| Notification capture | WinRT | dbus (Linux) |
-| Monitor names | Friendly names (WMI) | Generic ("Display 0") |
-| Automation: window/process conditions | Supported | Partial |
+| Feature | Windows | Linux / macOS | Android TV (experimental) |
+| ------- | ------- | ------------- | ------------------------- |
+| Screen capture | DXCam, BetterCam, WGC, MSS | MSS | MediaProjection; root `screenrecord` (rooted devices) |
+| Webcam capture | OpenCV (DirectShow) | OpenCV (V4L2) | — (no OpenCV wheel) |
+| Audio capture | WASAPI, Sounddevice | Sounddevice (PulseAudio/PipeWire) | AudioPlaybackCapture (API 29+) |
+| GPU monitoring | NVIDIA (nvidia-ml-py) | NVIDIA (nvidia-ml-py) | — (CPU/RAM/battery/thermal via `/proc`) |
+| Capture from Android phone | scrcpy (ADB) | scrcpy (ADB) | — (captures its own screen instead) |
+| Notification capture | WinRT | dbus (Linux) | NotificationListenerService |
+| Monitor names | Friendly names (WMI) | Generic ("Display 0") | Single built-in display |
+| LED transports | Network, USB-serial, BLE | Network, USB-serial, BLE | Network, USB-serial (Android driver), BLE (Android bridge) |
+| Automation: window/process conditions | Supported | Partial | — |
 
 ## Requirements