harmonia: /var/lib/dotfiles-deploy → /var/lib/nix-deploy

URL contract (https://nix-cache.sigkill.computer/deploy/<host>) is preserved;
only the on-disk Caddy root and the tmpfiles directory change. Phase 6 seeds
/var/lib/nix-deploy/ from the old path before deploying the new config, so the
pull-update on yarn stays working across the cutover.

services/harmonia.nix

@@ -18,10 +18,10 @@
   };
 
   # serve latest deploy store paths (unauthenticated — just a path string)
-  # CI writes to /var/lib/dotfiles-deploy/<hostname> after building
+  # CI writes to /var/lib/nix-deploy/<hostname> after building
   services.caddy.virtualHosts."nix-cache.${service_configs.https.domain}".extraConfig = ''
     handle_path /deploy/* {
-        root * /var/lib/dotfiles-deploy
+        root * /var/lib/nix-deploy
         file_server
     }
 
@@ -33,6 +33,6 @@
 
   # directory for CI to record latest deploy store paths
   systemd.tmpfiles.rules = [
-    "d /var/lib/dotfiles-deploy 0755 gitea-runner gitea-runner"
+    "d /var/lib/nix-deploy 0755 gitea-runner gitea-runner"
   ];
 }