Resolve all statix and nixpkgs-fmt warnings repo-wide

Zero W20 (repeated attribute keys), W10 (empty { ... }: variadic
pattern, use _: instead), and W04 (a = x.a instead of inherit)
warnings remain anywhere in the tree, and nixpkgs-fmt --check is
clean on all 46 .nix files.

Repeated-key merges go as deep as statix actually flags per file
(e.g. boot.loader.* nested under boot.loader = { ... } once the
outer boot.* merge exposed it as its own repeat) — every merge is a
pure attribute-path restructuring with no value changes, verified by
comparing config.system.build.toplevel.drvPath before/after for a
representative host per changed module plus a full 19-host + 4-package
eval sweep.

One indentation slip caught and fixed during this pass: nesting
modules/installer/common.nix's environment.etc."auto-install.sh".text
under an environment = { ... } block initially normalized the
script's shebang/set line indentation, which actually changes the
rendered file (Nix's '' string dedent treats it as real content, not
cosmetic whitespace) — reproduced the original's exact indentation
and reverified the rendered script is byte-identical to before.

modules/services/zfs/auto-mount-volumes.nix picked up formatting too;
worth noting it isn't imported by anything in this flake at all.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01La55Nsss8jZ7ZuzUV9mfot

modules/build-types/pxe-boot.nix

@@ -95,28 +95,32 @@ in
     ipxe
   ];
 
-  services.nginx = {
-    enable = true;
+  services = {
+    nginx = {
+      enable = true;
 
-    virtualHosts."pxe-boot" = {
-      default = true;
-      root = httpRoot;
-      locations."/" = {
-        extraConfig = ''
-          autoindex on;
-        '';
+      virtualHosts."pxe-boot" = {
+        default = true;
+        root = httpRoot;
+        locations."/" = {
+          extraConfig = ''
+            autoindex on;
+          '';
+        };
       };
     };
-  };
 
-  # TFTP is only used to deliver the initial iPXE bootloader. After iPXE
-  # starts, all further assets are fetched via nginx over HTTP.
-  services.atftpd = {
-    enable = true;
-    root = tftpRoot;
-    extraOptions = [
-      "--verbose=5"
-    ];
+    # TFTP is only used to deliver the initial iPXE bootloader. After iPXE
+    # starts, all further assets are fetched via nginx over HTTP.
+    atftpd = {
+      enable = true;
+      root = tftpRoot;
+      extraOptions = [
+        "--verbose=5"
+      ];
+    };
+
+    openssh.settings.PermitRootLogin = "yes";
   };
 
   systemd.tmpfiles.rules = [
@@ -149,8 +153,6 @@ in
     };
   };
 
-  services.openssh.settings.PermitRootLogin = "yes";
-
   networking.firewall.allowedTCPPorts = [ 80 ];
   networking.firewall.allowedUDPPorts = [ 69 ];
 }