Heatmap solver is now a worker

- Android app now requests root (purpose still unknown)
- Android app starts on boot
- Frontend is now a PWA (purpose still unknown)

frontend/src/app/map/map.component.html

@@ -23,4 +23,17 @@
         source="lastLoc"
         [paint]="lastLocationPaint"
     ></mgl-layer>
+    <div class="controls">
+      <mgl-control *ngIf="heatmapPending">
+        Compute heat map, please wait ...
+      </mgl-control>
+      <mgl-control
+        mglNavigation
+      ></mgl-control>
+      <mgl-control
+        mglScale
+        unit="metric"
+        position="top-right"
+      ></mgl-control>
+    </div>
 </mgl-map>