fix(mihomo): order the service after its config mount (#382)

The config deliberately stays out of the store, under the home directory, which is a persistent bind mount on tmpfs-root hosts. When the service and the mount are introduced in the same activation, mihomo can start before the mount is up and fail with "Failed to set up credentials: No such file or directory", making the switch report status 4. Add RequiresMountsFor so the mount is brought up and ordered before the service.

modules/nixos/desktop/networking/mihomo/default.nix

@@ -31,5 +31,11 @@ in
       webui = pkgs.metacubexd;
       tunMode = true;
     };
+
+    # The config deliberately stays out of the store, under the user's home. On
+    # tmpfs-root hosts that path is a persistent bind mount, so make the service
+    # wait for it: otherwise activation can start mihomo before the mount is up
+    # and fail with "Failed to set up credentials: No such file or directory".
+    systemd.services.mihomo.unitConfig.RequiresMountsFor = builtins.dirOf configFile;
   };
 }