fix(argo): bump fxcache memory to 96Gi (OOM at 56Gi with 28 chunks)

Alpha feature pipeline runs 28 parallel chunks across 17.8M imbalance
bars, peaking at ~70GB RSS. Previous 56Gi limit caused OOMKill.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

infra/k8s/argo/train-multi-seed-template.yaml

@@ -353,10 +353,10 @@ spec:
         resources:
           requests:
             cpu: "4"
-            memory: 16Gi
+            memory: 32Gi
           limits:
             cpu: "28"
-            memory: 56Gi
+            memory: 96Gi
         volumeMounts:
           - name: training-data
             mountPath: /data