fix(gitops): mount nxtgauge-uploads-pvc into nxtgauge-rust-companies for B2 fallback storage

Wire the local-disk fallback path so companies service can write documents
when Backblaze B2 is unavailable (B2 outage under investigation).

apps/nxtgauge-backend-rust/overlays/prod/companies-volume-patch.yaml

@@ -0,0 +1,16 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nxtgauge-rust-companies
+spec:
+  template:
+    spec:
+      volumes:
+        - name: nxtgauge-uploads
+          persistentVolumeClaim:
+            claimName: nxtgauge-uploads-pvc
+      containers:
+        - name: companies
+          volumeMounts:
+            - name: nxtgauge-uploads
+              mountPath: /var/lib/nxtgauge-uploads

apps/nxtgauge-backend-rust/overlays/prod/kustomization.yaml

@@ -5,3 +5,7 @@ resources:
   - ../../base
 patches:
   - path: release-patches.yaml
+  - path: companies-volume-patch.yaml
+    target:
+      kind: Deployment
+      name: nxtgauge-rust-companies