Fix container to run app as routewatch user

Use runuser to drop privileges and execute the app as the routewatch
user (uid 1000). Fix data directory permissions at runtime since host
mounts may have incorrect ownership.

entrypoint.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+cd /var/lib/berlin.sneak.app.routewatch
+chown -R routewatch:routewatch .
+chmod 700 .
+
+exec runuser -u routewatch -- /app/routewatch