feat: add nixpkgs-unstable flake input

flake.lock

@@ -50,6 +50,22 @@
         "type": "github"
       }
     },
+    "nixpkgs-unstable": {
+      "locked": {
+        "lastModified": 1751271578,
+        "narHash": "sha256-P/SQmKDu06x8yv7i0s8bvnnuJYkxVGBWLWHaU+tt4YY=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "3016b4b15d13f3089db8a41ef937b13a9e33a8df",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
     "nixpkgs_2": {
       "locked": {
         "lastModified": 1750259320,
@@ -70,7 +86,8 @@
       "inputs": {
         "home-manager": "home-manager",
         "nixos-hardware": "nixos-hardware",
-        "nixpkgs": "nixpkgs_2"
+        "nixpkgs": "nixpkgs_2",
+        "nixpkgs-unstable": "nixpkgs-unstable"
       }
     }
   },

flake.nix

@@ -1,11 +1,12 @@
 {
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.05";
+    nixpkgs-unstable.url = "github:NixOS/nixpkgs/nixos-unstable";
     home-manager.url = "github:nix-community/home-manager/release-25.05";
     nixos-hardware.url = "github:NixOS/nixos-hardware";
   };
 
-  outputs = inputs @ { self, nixpkgs, ... }: {
+  outputs = inputs @ { self, nixpkgs, nixpkgs-unstable, ... }: {
     nixosConfigurations.affogato = nixpkgs.lib.nixosSystem {
       system = "x86_64-linux";
       modules = [