Initial NixOS flake-based multi-host setup

Add a NixOS system configuration using flakes, supporting multiple hosts (desktop, laptop, my-machine) with shared and per-host settings. Includes Home Manager integration, user-level and system-level package management, and example hardware configuration placeholders. Provides a README with setup instructions and a .gitignore for common Nix and editor artifacts.

flake.lock

@@ -0,0 +1,49 @@
+{
+  "nodes": {
+    "home-manager": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1,
+        "narHash": "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=",
+        "owner": "nix-community",
+        "repo": "home-manager",
+        "rev": "0000000000000000000000000000000000000000",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "ref": "release-25.05",
+        "repo": "home-manager",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1729618870,
+        "narHash": "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "879bd460b3d3bb3c4c67e863af2c3a7dbbebb87e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-25.05",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "home-manager": "home-manager",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}