Add linting, formatting, and CI with fixes for all warnings

Infrastructure:
- Add deadnix, nixfmt, and statix to flake inputs
- Add formatter output to flake for nix fmt support
- Add deadnix, nixfmt, statix to Home Manager packages
- Add GitHub Actions workflow for CI validation
- Add .pre-commit-config.yaml with hooks for nixfmt, deadnix, and statix
- Support x86_64-darwin in formatter

Statix fixes (W10/W20 warnings):
- Remove unused lambda argument from nixpkgs-settings.nix
- Merge repeated keys in hardware-configuration.nix files (boot.initrd, boot, fileSystems)
- Merge repeated keys in nixnuc/default.nix (services, virtualisation)
- Merge repeated keys in rainbow-planet/default.nix (desktopManager)
- Merge repeated keys in home/general/default.nix (home)

Deadnix fixes (unused declarations):
- Remove unused pkgs/lib/username/http_port arguments from various files
- Fix unused final parameter in overlay functions (final -> _final)

CI/pre-commit fixes:
- Fix pre-commit statix config: add pass_filenames: false
- Fix CI workflow: use nix run nixpkgs# prefix and --ci flag for nixfmt

modules/hosts/nixos/hetznix01/post-install/nginx.nix

@@ -1,9 +1,11 @@
-{ config, ... }: let
+{ config, ... }:
+let
   domain = "technicalissues.us";
   http_port = 80;
   https_port = 443;
   private_btc = "umbrel.atlas-snares.ts.net";
-in {
+in
+{
 
   services.nginx = {
     enable = true;
@@ -134,14 +136,36 @@ in {
       };
       "matrix.${domain}" = {
         listen = [
-          { port = http_port; addr = "0.0.0.0"; }
-          { port = http_port; addr = "[::]"; }
+          {
+            port = http_port;
+            addr = "0.0.0.0";
+          }
+          {
+            port = http_port;
+            addr = "[::]";
+          }
 
-          { port = https_port; addr = "0.0.0.0"; ssl = true; }
-          { port = https_port; addr = "[::]"; ssl = true; }
+          {
+            port = https_port;
+            addr = "0.0.0.0";
+            ssl = true;
+          }
+          {
+            port = https_port;
+            addr = "[::]";
+            ssl = true;
+          }
 
-          { port = 8448; addr = "0.0.0.0"; ssl = true; }
-          { port = 8448; addr = "[::]"; ssl = true; }
+          {
+            port = 8448;
+            addr = "0.0.0.0";
+            ssl = true;
+          }
+          {
+            port = 8448;
+            addr = "[::]";
+            ssl = true;
+          }
         ];
         enableACME = true;
         acmeRoot = null;
@@ -195,7 +219,8 @@ in {
           "/" = {
             proxyPass = "http://127.0.0.1:8083";
           };
-          "/pub" = { # Client apps need to point to this path
+          "/pub" = {
+            # Client apps need to point to this path
             extraConfig = "proxy_set_header X-Limit-U $remote_user;";
             proxyPass = "http://127.0.0.1:8083/pub";
           };