Add best-effort geolocation to the IP lookup from geojs and DB-IP City Lite (closes #239)

Each result gains `geo`. One request to geojs carries every address, 1 second in all. On a timeout, an error or an answer with no country, city or coordinates, the lookup reads DB-IP City Lite, downloaded monthly into the state directory. geojs answers stay in memory (250,000, least recently used dropped) and in a new `cache.db` table for 7 days.

Judgement call: a reserved address goes to neither source, and its `geo` is null.
Judgement call: `updated` for DB-IP is when the copy was downloaded.
Deviation: the cache is SQLite, by sneak's words.

Model: opus-5-5

Dockerfile

@@ -105,7 +105,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 ARG CACHEBUST
 
 # Create non-root user
-RUN useradd -u 1000 -m routewatch
+RUN useradd -r -u 1000 -m routewatch
 
 RUN mkdir -p /var/lib/berlin.sneak.app.routewatch && chown routewatch:routewatch /var/lib/berlin.sneak.app.routewatch
 

TODO.md

@@ -53,12 +53,6 @@ problem the run finds.
 
 # Completed Steps
 
-- 2026-11-10: `github.com/mattn/go-sqlite3` is at v1.14.53, so building on the
-  host no longer prints its two C compiler warnings (closes
-  https://git.eeqj.de/sneak/routewatch/issues/245).
-- 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

go.mod

@@ -9,7 +9,7 @@ require (
 	github.com/google/btree v1.1.3
 	github.com/google/uuid v1.6.0
 	github.com/hashicorp/golang-lru/v2 v2.0.7
-	github.com/mattn/go-sqlite3 v1.14.53
+	github.com/mattn/go-sqlite3 v1.14.29
 	github.com/maxmind/mmdbwriter v1.2.0
 	github.com/miekg/dns v1.1.73
 	github.com/oschwald/maxminddb-golang/v2 v2.9.0

go.sum

@@ -10,8 +10,8 @@ github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/hashicorp/golang-lru/v2 v2.0.7 h1:a+bsQ5rvGLjzHuww6tVxozPZFVghXaHOwFs4luLUK2k=
 github.com/hashicorp/golang-lru/v2 v2.0.7/go.mod h1:QeFd9opnmA6QUJc5vARoKUSoFhyfM2/ZepoAG6RGpeM=
-github.com/mattn/go-sqlite3 v1.14.53 h1:mnTM0owzUMrKuLo+0w51NUiB0ir2Fo7kFXlPt/l3BGs=
-github.com/mattn/go-sqlite3 v1.14.53/go.mod h1:6JTjA44L93a0QCyJef5YvlPoKXntQPjzWv5gtm9sB6w=
+github.com/mattn/go-sqlite3 v1.14.29 h1:1O6nRLJKvsi1H2Sj0Hzdfojwt8GiGKm+LOfLaBFaouQ=
+github.com/mattn/go-sqlite3 v1.14.29/go.mod h1:Uh1q+B4BYcTPb+yiD3kU8Ct7aC0hY9fxUwlHK0RXw+Y=
 github.com/maxmind/mmdbwriter v1.2.0 h1:hyvDopImmgvle3aR8AaddxXnT0iQH2KWJX3vNfkwzYM=
 github.com/maxmind/mmdbwriter v1.2.0/go.mod h1:EQmKHhk2y9DRVvyNxwCLKC5FrkXZLx4snc5OlLY5XLE=
 github.com/miekg/dns v1.1.73 h1:uhT8nJxmTrPJYClxVxTCX+CVn6qnzSiybRk72Z6DgrE=