router: fix unbound restarting on any flake update

flake.lock

@@ -198,7 +198,6 @@
       "original": {
         "owner": "chayleaf",
         "repo": "nixos-router",
-        "rev": "b28e10ec8d247babd9ff461bb14725e504d3badf",
         "type": "github"
       }
     },

system/hosts/router/default.nix

@@ -670,7 +670,9 @@ in {
             ''"${domain}. AAAA ${serverAddress6}"''
           ]) hosted-domains);
       };
-      python.python-script = toString ./avahi-resolver-v2.py;
+      # normally it would refer to the flake path, but then the service changes on every flake update
+      # instead, write a new file in nix store
+      python.python-script = builtins.toFile "avahi-resolver-v2.py" (builtins.readFile ./avahi-resolver-v2.py);
       remote-control.control-enable = true;
     };
   };