Migrate to clean package-only structure

- Simplified flake.nix to focus only on packaging Cursor
- Removed system configuration files (archived locally)
- Updated to clean, reusable flake structure
- Added simple update-cursor.sh script
- Updated documentation for new structure

This migration  makes the flake purely focused on providing the Cursor package.

flake.lock

@@ -1,25 +1,5 @@
 {
   "nodes": {
-    "home-manager": {
-      "inputs": {
-        "nixpkgs": [
-          "nixpkgs"
-        ]
-      },
-      "locked": {
-        "lastModified": 1754421590,
-        "narHash": "sha256-TrlzGR5l/OltcTnBtihUxoKqv+JNEKWmUamDVWICtX0=",
-        "owner": "nix-community",
-        "repo": "home-manager",
-        "rev": "a0b1afdb5efbf59f4b6e934d090cf8d150517890",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-community",
-        "repo": "home-manager",
-        "type": "github"
-      }
-    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1754214453,
@@ -38,7 +18,6 @@
     },
     "root": {
       "inputs": {
-        "home-manager": "home-manager",
         "nixpkgs": "nixpkgs"
       }
     }