chore: add .env.example for Nominatim stack

.env.example

@@ -0,0 +1,17 @@
+# Copy to .env and edit. docker compose reads .env automatically.
+
+# Filename of the .osm.pbf under ./data/ (mounted read-only into the container).
+# Reuse the same Geofabrik extract as OSRM — symlink or copy the PBF here.
+# Do NOT point this at OSRM .osrm* graph files.
+NOMINATIM_PBF_FILE=region.osm.pbf
+
+# Required. Change from the mediagis default before exposing on the LAN.
+NOMINATIM_PASSWORD=change-me
+
+# Host address to bind the API on. Default 0.0.0.0 serves the homelab LAN
+# (10.0.0.0/24). Use 127.0.0.1 for local-only on this machine.
+NOMINATIM_BIND_HOST=0.0.0.0
+
+# Import parallelism and Docker shm (raise for large extracts).
+NOMINATIM_THREADS=4
+NOMINATIM_SHM_SIZE=1gb