fix(nixConfig): deduplicate list values at type level instead of mkForce

Replace listOf with a custom deduplicatedListOf type that calls
lib.unique on the merged result, preventing duplicate entries from
nixConfig.settings propagation without resorting to mkForce (which
would prevent end-user overrides at the component level).

The deduplication runs during type merge, cleaning up duplicates
introduced when top-level nixConfig.settings are propagated to
subcomponents (node, pynixd controller, builder) via direct
assignment, where they merge with the submodule defaults at the
same priority.

Author: Lillecarl

kubenix/nixOptions.nix

@@ -13,6 +13,15 @@ let
     # "kvm"
   ];
 
+  deduplicatedListOf = type:
+    let
+      listType = lib.types.listOf type;
+      baseMerge = listType.merge;
+    in
+    listType // {
+      merge = loc: defs: lib.unique (baseMerge loc defs);
+    };
+
   semanticConfType =
     with lib.types;
     let
@@ -29,7 +38,7 @@ let
           description = "Nix config atom (null, bool, int, float, str, path or package)";
         };
     in
-    attrsOf (either confAtom (listOf confAtom));
+    attrsOf (either confAtom (deduplicatedListOf confAtom));
 in
 with lib;
 types.submodule (