Change default PocketBase port to 8070

Set the default listen/host port to 8070 across both the rootless and
root stacks (previously 8080 rootless / 8081 root). Both internal and
external mappings derive from the same PB_PORT/PB_PORT_ROOT variables,
so a single change covers container and host.

Updated .env.example, both Dockerfiles (ENV/EXPOSE), both compose files
(env, port mapping, healthcheck), and both entrypoint fallbacks.

Note: both stacks now default to host port 8070, so they can no longer
run simultaneously without overriding PB_PORT_ROOT.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

entrypoint.root.sh

@@ -6,7 +6,7 @@ set -e
 
 DATA_DIR="/pb/pb_data"
 DB_FILE="${DATA_DIR}/data.db"
-PB_PORT="${PB_PORT:-8080}"
+PB_PORT="${PB_PORT:-8070}"
 
 # ---- assemble global flags shared by every pocketbase invocation ----
 set -- --dir="${DATA_DIR}"