Fix init container: use externalDatabase password instead of missing secret

The init-db-config container was referencing a non-existent secret
{namespace}-os-schedules-argo-syncer-mysql, causing CreateContainerConfigError.
Now reads password directly from .Values.externalDatabase.password.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

helm/schedulerservice/templates/deployment.yaml

@@ -75,10 +75,7 @@ spec:
               echo "MySQL is fully initialized!"
           env:
             - name: MYSQL_PASSWORD
-              valueFrom:
-                secretKeyRef:
-                  name: {{ .Release.Namespace }}-os-schedules-argo-syncer-mysql
-                  key: mysql-password
+              value: {{ .Values.externalDatabase.password | quote }}
           volumeMounts:
             - name: db-config
               mountPath: /db-config