fix: add legacy role label to MongoDB pod for NetworkPolicy compatibility

MongoDB pods require the 'role: database-eagle-epic' label for the
eagle-epic-allow-services-to-database NetworkPolicy to allow
eagle-api pods to connect on port 27017.

Author: danieltruong

helm/eagle-api/templates/mongodb-deployment.yaml

@@ -18,6 +18,7 @@ spec:
     metadata:
       labels:
         {{- include "eagle-api.mongodb.selectorLabels" . | nindent 8 }}
+        role: database-eagle-epic  # Legacy label required by NetworkPolicy
     spec:
       containers:
       - name: mongodb