Initial commit: restic backup configuration

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

flake.nix

@@ -0,0 +1,20 @@
+{
+  description = "Restic backup for starbak -> thalassa.local";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  };
+
+  outputs = { self, nixpkgs }:
+    let
+      system = "aarch64-darwin";
+      pkgs = nixpkgs.legacyPackages.${system};
+    in
+    {
+      devShells.${system}.default = pkgs.mkShell {
+        packages = [
+          pkgs.restic
+        ];
+      };
+    };
+}