Add Go compiler; split system.nix into focused modules

system.nix had grown to 200 lines covering boot, networking, locale,
audio, Bluetooth, fonts, nix settings, hardening, DNS and RGB. Split it
by concern into boot.nix, networking.nix, locale.nix, nix-settings.nix,
security.nix and audio.nix.

Also:
- drivers.nix -> hardware.nix, absorbing Bluetooth, the I2C udev rule,
  OpenRGB and printing
- fonts -> desktop.nix
- nix-ld and pkgs.file -> apps.nix
- the Bottles tmpfiles link -> users.nix, next to services.flatpak

The reorganization is behavior-neutral: the dbus-1, system-units,
user-units and system-path trees are byte-identical to the previous
build once self-referential store paths are normalized, and
`nix store diff-closures` against the running system reports exactly
one change -- go 1.26.7.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

modules/apps.nix

@@ -70,6 +70,7 @@ in
     gcc
     python3
     openjdk25
+    go
     claude-code
   ];
 
@@ -100,5 +101,17 @@ in
     qt5.qtwayland
     qt6.qtwayland
     qemu
+    file
+  ];
+
+  # Lets non-Nix binaries (e.g. the Tor Browser bundle) find an FHS linker.
+  programs.nix-ld.enable = true;
+  programs.nix-ld.libraries = with pkgs; [
+    glib gtk3 gdk-pixbuf pango cairo atk
+    dbus dbus-glib fontconfig freetype
+    libx11 libxext libxrender libxtst
+    libxi libxcomposite libxdamage libxfixes
+    libxrandr libxcursor libxcb libxkbcommon
+    alsa-lib mesa zlib stdenv.cc.cc
   ];
 }