ci: bootstrap nix on hosted runners before deploy

.forgejo/workflows/deploy-cloudflare.yml

@@ -20,6 +20,9 @@ jobs:
           CLOUDFLARE_API_TOKEN: ${{ secrets.CLOUDFLARE_API_TOKEN }}
         run: |
           set -euo pipefail
-          pwd
-          ls -la
+          if ! command -v nix >/dev/null 2>&1; then
+            curl -L https://nixos.org/nix/install | sh -s -- --no-daemon
+            . "$HOME/.nix-profile/etc/profile.d/nix.sh"
+          fi
+          nix --version
           ./scripts/deploy-workers.sh