fix(infra): lob-backtest-sweep volume claim name training-data -> training-data-pvc

The template referenced PVC 'training-data' but the actual claim in
the foxhunt namespace is 'training-data-pvc' (matches the convention
used by other workflows like alpha-perception-template). Without this
fix, ensure-binary + run-cell + aggregate pods all stayed Pending
forever with 'persistentvolumeclaim "training-data" not found',
blocking every smoke / threshold-tuning / deployability sweep.

Verified: smoke sweep lob-backtest-sweep-jp48v scheduled ensure-binary
onto the ci-compile-cpu pool (autoscaler triggered scale-up 0->1
within seconds of resubmission).

infra/k8s/argo/lob-backtest-sweep-template.yaml

@@ -91,7 +91,7 @@ spec:
   volumes:
     - name: training-data
       persistentVolumeClaim:
-        claimName: training-data
+        claimName: training-data-pvc
     - name: git-ssh-key
       secret:
         secretName: git-ssh-key