Add bear + QR app icon

A green icon where a QR code's finder squares form a bear face — brown ears on
top, cream snout in the center. Wired as the main icon, the Android adaptive
icon (foreground + #0f1a12 background), and the web/PWA icons + favicon.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/app.json

@@ -7,9 +7,14 @@
     "scheme": "campscan",
     "userInterfaceStyle": "automatic",
     "newArchEnabled": true,
+    "icon": "./assets/icon.png",
     "android": {
       "package": "top.mowden.campscan",
       "versionCode": 1,
+      "adaptiveIcon": {
+        "foregroundImage": "./assets/adaptive-icon.png",
+        "backgroundColor": "#0f1a12"
+      },
       "permissions": [
         "android.permission.CAMERA",
         "android.permission.VIBRATE"