manatee: Wait for ZFS mounts before starting sandboxed /mnt/media services

hosts/manatee/modules/transmission/default.nix

@@ -52,5 +52,12 @@ in
         };
       };
     };
+
+    # Both paths are bind mounted into the service's own mount namespace when it
+    # starts, so starting before the ZFS dataset is mounted writes to the root disk
+    systemd.services.transmission.unitConfig.RequiresMountsFor = [
+      config.services.transmission.home
+      config.services.transmission.settings.download-dir
+    ];
   };
 }