feat: add niks3 to ci

.forgejo/workflows/build.yaml

@@ -7,8 +7,16 @@ jobs:
     runs-on: [ nix ]
     steps:
     - uses: actions/checkout@v4
+    - name: niks3 setup
+      uses: https://git.tami.moe/actions/niks3-upload@main
+      with:
+        token: ${{ secrets.NIKS3_TOKEN }}
     - name: Nix build
-      run: nix build --extra-experimental-features "flakes nix-command" .#docker-image
+      run: |
+        nix build --extra-experimental-features "flakes nix-command" .#deps
+        niks3 push --pin "$FORGEJO_REPOSITORY-deps" $(readlink result)
+        nix build --extra-experimental-features "flakes nix-command" .#docker-image
+        niks3 push --pin "$FORGEJO_REPOSITORY-container" $(readlink result)
     - name: Setup skopeo
       run: curl -o /etc/containers/policy.json --create-dirs https://raw.githubusercontent.com/containers/skopeo/refs/heads/main/default-policy.json
     - name: Push Image