fix(attic): specify PostgreSQL database for postStart script

- Update `psql` command in the `postStart` script to explicitly connect to the `postgres` database before altering ownership of the `attic` database.
- Ensures the command runs without issues in environments with restricted default database access.

systems/x86_64-linux/attic/atticd.nix

@@ -8,11 +8,11 @@
   services.postgresql = {
     enable = true;
     ensureDatabases = [ "attic" ];
-    ensureUsers = [ { name = "atticd"; } ];
+    ensureUsers = [{ name = "atticd"; }];
   };
 
   systemd.services.postgresql.postStart = lib.mkAfter ''
-    psql -tAc 'ALTER DATABASE "attic" OWNER TO "atticd"'
+    psql -d postgres -tAc 'ALTER DATABASE "attic" OWNER TO "atticd"'
   '';
 
   environment.systemPackages = with pkgs; [ attic-client ];