Create the image's app user without the system-user flag (closes #248)

`useradd -r` with UID 1000 made the image build warn, since 1000 is above the system range. The user keeps UID 1000, so the data directory's owner does not change.

Model: opus-5-5

TODO.md

@@ -53,6 +53,9 @@ problem the run finds.
 
 # Completed Steps
 
+- 2026-11-10: the image creates the `routewatch` user as a regular user with UID
+  1000, so the build no longer warns about the system UID range (closes
+  https://git.eeqj.de/sneak/routewatch/issues/248).
 - 2026-11-10: each result of the IP lookup has `geo`, where the address is. It
   comes from geojs, with DB-IP's City Lite database as the fallback. The geojs
   answers stay in memory and in `cache.db` for 7 days (closes