fix(neuron-stage): set NEURON_DATA_DIR=/data for persistent Kotlin DB

The Kotlin NeuronModule reads NEURON_DATA_DIR to locate the SQLite file.
The stage configmap only had NEURON_DB_PATH/NEURON_STORAGE_PATH which
the Kotlin code doesn't read, causing it to fall back to a temp file
that was wiped on every pod restart.

Adding NEURON_DATA_DIR=/data ensures the server reads from the persistent
PVC-backed /data/neuron.db going forward.

servers/legion/k8s/neuron-technologies/stage/configmap.yaml

@@ -5,7 +5,8 @@ metadata:
   namespace: neuron-stage
 data:
   SPRING_PROFILES_ACTIVE: "stage"
-  NEURON_DB_PATH: "/data/neuron-stage.db"
+  NEURON_DATA_DIR: "/data"
+  NEURON_DB_PATH: "/data/neuron.db"
   NEURON_STORAGE_PATH: "/data"
   SERVER_TOMCAT_ACCESSLOG_ENABLED: "true"
   # Stage: extended for pre-prod verification, not fully open