feat(storage): migrate SeaweedFS S3 credentials to VSO; mount s3.json from Secret

Previously s3.json was embedded in the seaweedfs-filer-config ConfigMap
with hardcoded minioadmin credentials, and the config volume was mounted
at /etc/seaweedfs/ (overwriting filer.toml with its own directory mount).

- Remove s3.json from ConfigMap; fix the config volume to mount only
  filer.toml via subPath so both files coexist under /etc/seaweedfs/.
- Add vault-secrets.yaml with VaultStaticSecrets that VSO syncs from
  OpenBao secret/seaweedfs: seaweedfs-s3-credentials (S3_ACCESS_KEY /
  S3_SECRET_KEY) and seaweedfs-s3-json (s3.json as a JSON template).
- Mount seaweedfs-s3-json Secret at /etc/seaweedfs/s3.json via subPath.

base/storage/seaweedfs-filer.yaml

@@ -38,7 +38,12 @@ spec:
                 name: seaweedfs-s3-credentials
           volumeMounts:
             - name: config
-              mountPath: /etc/seaweedfs
+              mountPath: /etc/seaweedfs/filer.toml
+              subPath: filer.toml
+              readOnly: true
+            - name: s3-json-secret
+              mountPath: /etc/seaweedfs/s3.json
+              subPath: s3.json
               readOnly: true
             - name: filer-data
               mountPath: /data/filer
@@ -52,6 +57,9 @@ spec:
         - name: config
           configMap:
             name: seaweedfs-filer-config
+        - name: s3-json-secret
+          secret:
+            secretName: seaweedfs-s3-json
         - name: filer-data
           emptyDir: {}
 ---