feat(nix): add LocalSend (file transfer), nixpkgs-fmt (formatter for .nix)

configuration.nix

@@ -9,7 +9,8 @@ let
 in
 {
   imports =
-    [ # Include the results of the hardware scan.
+    [
+      # Include the results of the hardware scan.
       ./hardware-configuration.nix
     ] ++ lib.optional (builtins.pathExists sshConfigPath) sshConfigPath;
 
@@ -20,6 +21,15 @@ in
 
   networking.hostName = "spy4x-pc";
   networking.networkmanager.enable = true;
+  networking = {
+    firewall = {
+      enable = true;
+      allowedTCPPorts = [
+        80 # Web server to debug apps from mobile
+        53317 # LocalSend
+      ];
+    };
+  };
 
   # Allow install "unfree" apps, like Google Chrome or WebStorm
   nixpkgs.config.allowUnfree = true;
@@ -89,6 +99,7 @@ in
       libwebp # Convert images into .webp format
       wl-clipboard # Wayland's clipboard copy/paste cli tools
       tree
+      nixpkgs-fmt # Formatter for .nix files. Like Prettier.
 
       # Work
       nodejs_21
@@ -106,6 +117,7 @@ in
       vlc
       obs-studio # Video recorder and stream software
       solaar # Logitech devices GUI. Strictly use with sudo, otherwise it doesn't see devices.
+      localsend # Share files/text/data with other devices in local network without internet. OSS alternative to AirDrop.
     ];
   };
   programs.steam.enable = true; # Install Steam for games management