Fix admin publish data loss for unreleased lessons and harden data persistence

entrypoint.sh

@@ -1,7 +1,7 @@
 #!/bin/sh
 set -e
 
-DATA_DIR=/app/data
+DATA_DIR=${SITEFORGE_DATA_DIR:-/app/data}
 SEED_DIR=/app/data-seed
 
 # Ensure the data directory exists (in case the volume was not mounted)
@@ -210,4 +210,5 @@ NODE
 merge_seed_study_release_dates "$DATA_DIR/admin-content.json" "$SEED_DIR/admin-content.json"
 merge_seed_study_release_dates "$DATA_DIR/admin-content-draft.json" "$SEED_DIR/admin-content-draft.json"
 
+export SITEFORGE_DATA_DIR="$DATA_DIR"
 exec node server.js