fix(opencloud): shrink backup pod requests to fit worker-3 (DEV-555)

The scheduled backup pod could not start because worker-3 (where the
opencloud data PVC is attached and where podAffinity pins the backup)
had ~40Mi of memory left by requests after opencloud/tika were
co-scheduled. rclone actually uses well under 100Mi during the sync.

Drop cpu request 100m -> 50m and memory request 256Mi -> 64Mi. Limits
unchanged (500m / 512Mi) so it can still burst.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/opencloud/backup-cronjob.yaml

@@ -90,8 +90,8 @@ spec:
               readOnly: true
             resources:
               requests:
-                memory: "256Mi"
-                cpu: "100m"
+                memory: "64Mi"
+                cpu: "50m"
               limits:
                 memory: "512Mi"
                 cpu: "500m"