feat: implement Attic binary cache with remote build support and sops-nix integration

.github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
       hosts: ${{ steps.hosts.outputs.hostnames }}
     steps:
       - uses: actions/checkout@v5
-      - uses: https://github.com/cachix/install-nix-action@v31
+      - uses: cachix/install-nix-action@v31
         with:
           nix_path: nixpkgs=channel:nixos-unstable
       - name: "Determine hosts"
@@ -34,10 +34,16 @@ jobs:
 
     steps:
       - uses: actions/checkout@v5
-      - uses: https://github.com/cachix/install-nix-action@v31
+      - uses: cachix/install-nix-action@v31
         with:
           nix_path: nixpkgs=channel:nixos-unstable
       - name: "Build host"
         run: |
           nix build ".#nixosConfigurations.${{ matrix.hostname }}.config.system.build.toplevel" --verbose
+      - name: "Push to Attic"
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        run: |
+          nix profile install nixpkgs#attic-client
+          attic login homelab http://192.168.0.25:8080 "${{ secrets.ATTIC_TOKEN }}"
+          attic push homelab result