feat: add Dockerfile to set up PostGIS with pg_cron for scheduled tasks

Author: jirhiker

docker/db/Dockerfile

@@ -0,0 +1,5 @@
+FROM postgis/postgis:17-3.5
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends postgresql-17-cron \
+    && rm -rf /var/lib/apt/lists/*