Flake: Export default overlay

Flake lock file updates:

• Updated input 'nixpkgs-unstable':
    'github:NixOS/nixpkgs/9df3e30ce24fd28c7b3e2de0d986769db5d6225d' (2024-03-06)
  → 'github:NixOS/nixpkgs/063dece00c5a77e4a0ea24e5e5a5bd75232806f8' (2025-04-06)

flake.lock

@@ -71,11 +71,11 @@
     },
     "nixpkgs-unstable": {
       "locked": {
-        "lastModified": 1709703039,
+        "lastModified": 1743964447,
-        "narHash": "sha256-6hqgQ8OK6gsMu1VtcGKBxKQInRLHtzulDo9Z5jxHEFY=",
+        "narHash": "sha256-nEo1t3Q0F+0jQ36HJfbJtiRU4OI+/0jX/iITURKe3EE=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "9df3e30ce24fd28c7b3e2de0d986769db5d6225d",
+        "rev": "063dece00c5a77e4a0ea24e5e5a5bd75232806f8",
         "type": "github"
       },
       "original": {

flake.nix

@@ -49,5 +49,9 @@
          sops-nix.nixosModules.sops
       ];
     };
+
+    overlays = {
+      default = applyOverlays [ unfree-overlay unstable-overlay python-overlay ];
+    };
   };
 }

machines/kcnhub/packages/office.nix

@@ -1,7 +1,7 @@
 { pkgs, ...}: {
   environment.systemPackages = with pkgs; [
     # Browsers:
-    firefox
+    unstable.firefox
     chromium
     # Document editting
     libreoffice