feat(app,android): a new icon, and a launcher label that fits

The icon follows proton-drive-linux's logo: a violet gradient tile with
a darker lower edge, and a white play mark with a soft shadow, cut into
the blocks a revision is fetched in. The SVG, the window PNG and the
Windows .ico are rendered from one source.

On Android it is an adaptive icon with a monochrome layer for themed
icons, and the notification glyph is the same mark. The app is named
"Proton Stream"; the launcher shows "Stream", since "proton-stream" was
cut to "proton-st…".

android/app/src/main/res/drawable/ic_notification_stream.xml

@@ -1,13 +1,16 @@
 <!--
   The status-bar glyph. Android tints small icons to a single colour and drops
-  everything that is not opaque, so this is the launcher mark reduced to one
-  white silhouette rather than the two-tone drawable.
+  everything that is not opaque, so this is the launcher's sliced play mark as
+  one white silhouette, scaled from the SVG's 128-unit space onto 24dp.
 -->
 <vector xmlns:android="http://schemas.android.com/apk/res/android"
     android:width="24dp" android:height="24dp"
     android:viewportWidth="24" android:viewportHeight="24">
-    <path
-        android:fillColor="#FFFFFFFF"
-        android:fillType="evenOdd"
-        android:pathData="M4,4h16v16h-16zM10,8.5l5.5,3.5 -5.5,3.5z" />
+    <group
+        android:pivotX="70" android:pivotY="62"
+        android:scaleX="0.37" android:scaleY="0.37"
+        android:translateX="-58" android:translateY="-50">
+        <clip-path android:pathData="M0,0h63v128h-63zM68.5,0h10v128h-10zM84,0h44v128h-44z" />
+        <path android:fillColor="#FFFFFFFF" android:pathData="M50,41.5v41a6,6 0,0 0,9.1 5.1l34.2,-20.5a6,6 0,0 0,0 -10.3L59.1,36.4A6,6 0,0 0,50 41.5z" />
+    </group>
 </vector>