Mount neuron-marketplace.db from PVC via subPath at /app/neuron-marketplace.db

App hard-codes relative path 'neuron-marketplace.db' from working dir /app.
Mount the PVC file at /app/neuron-marketplace.db via subPath so the app can
write to it as UID 1000. PVC persists the file across pod restarts.
Also keep NEURON_MARKETPLACE_DB_PATH in ConfigMap for future app versions.

servers/legion/k8s/neuron-technologies/prod/mcp-deployment.yaml

@@ -22,7 +22,7 @@ spec:
         slot: blue
         env: prod
       annotations:
-        config-hash: "marketplace-db-path-v1"
+        config-hash: "marketplace-db-subpath-v2"
     spec:
       terminationGracePeriodSeconds: 30
       securityContext:
@@ -67,6 +67,9 @@ spec:
           volumeMounts:
             - name: data
               mountPath: /data
+            - name: data
+              mountPath: /app/neuron-marketplace.db
+              subPath: neuron-marketplace.db
           resources:
             requests:
               cpu: 250m