feat(4): Replace workflow with three

.forgejo/workflows/nightly.yml

@@ -0,0 +1,31 @@
+name: Nightly
+
+on:
+  schedule:
+    - cron: '0 2 * * *'
+
+jobs:
+  build:
+    runs-on: self-hosted
+    steps:
+      - uses: actions/checkout@v4
+      - name: Build
+        run: nix shell nixpkgs#mdbook --command ./deploy.sh build
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: site-${{ github.sha }}
+          path: blog/
+          retention-days: 1
+
+  deploy:
+    needs: build
+    runs-on: self-hosted
+    steps:
+      - name: Download artifact
+        uses: actions/download-artifact@v4
+        with:
+          name: site-${{ github.sha }}
+          path: blog/
+      - name: Deploy
+        run: nix shell nixpkgs#rsync --command ./deploy.sh local