feat: media send/receive (intent-based + notification bridge)

- POST /messages/send-media: multipart upload + adb push + intent + Appium
- Webhook mediaType: image detection + adb pull + fanout met download-url
- Download endpoint /download/:token (10 min TTL, cleanup every 5 min)
- Android NotificationListener: detecteert media-notificaties (lege/emoji text)
- Dockerfile: adb toegevoegd voor push/pull
- MEDIA_WAIT_MS env var (default 8000ms) voor pull-timing

wa-appium-api/package.json

@@ -5,6 +5,7 @@
   "main": "server.js",
   "dependencies": {
     "express": "^4.21.0",
-    "webdriverio": "^8.40.0"
+    "webdriverio": "^8.40.0",
+    "multer": "^1.4.5-lts.1"
   }
 }