feat(attic): update storage config and refine system settings

- Switch disk device from `/dev/vda` to `/dev/sda` for compatibility.
- Add S3 storage configuration with bucket, region, and endpoint.
- Update system state version from `24.05` to `25.11`.
- Remove unused imports and clean up redundant attributes.

systems/x86_64-linux/attic/default.nix

@@ -0,0 +1,36 @@
+{
+  ...
+}:
+{
+  imports = [
+    ./hardware-configuration.nix
+    ./atticd.nix
+  ];
+
+  metacfg = {
+    base.enable = true;
+    nix.enable = true;
+  };
+
+  system.autoUpgrade = {
+    enable = true;
+    operation = "switch";
+    allowReboot = true;
+  };
+
+  virtualisation = {
+    docker.enable = true;
+    podman.dockerCompat = false;
+  };
+
+  security.tpm2.enable = false;
+  security.tpm2.abrmd.enable = false;
+
+  networking.wireless.enable = false;
+  networking.firewall.allowedTCPPorts = [ 8080 ];
+  networking.firewall.allowPing = true;
+
+  powerManagement.cpuFreqGovernor = "ondemand";
+
+  system.stateVersion = "25.11";
+}