refactor: major architectural restructure for theme-centric organization

Theme System:
- Move all theme app configs to apps/ subdirectory (20 themes)
- Add theme-loader.nix for dynamic theme config deployment
- Simplify stylix.nix to focus on base theming only

Override System:
- Add overrides.nix for file-based config overrides
- Add behavior-configs.nix for non-visual configuration
- Split hypr/nomarchy.conf into behavior vs visual sections

Module Improvements:
- Add lib.mkDefault to all customizable settings
- Add modules/lib/ with shared utilities and state schema
- Update all home and system modules for downstream overridability

Installer:
- New minimal TTY installer (installer/install.sh)
- Golden path: BTRFS + LUKS2 (disko-golden.nix)
- New installer-iso.nix for TTY-only installation
- Keep graphical installer as installerIsoGraphical option

Cleanup:
- Remove obsolete install.sh, disko-ext4.nix, install-nomarchy.sh
- Update live-iso.nix references
- Add .claude/ to .gitignore for local IDE settings

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

modules/system/sddm.nix

@@ -18,11 +18,11 @@ let
   };
 in
 {
-  services.xserver.enable = true;
+  services.xserver.enable = lib.mkDefault true;
   services.displayManager.sddm = {
-    enable = true;
-    wayland.enable = true;
-    theme = "nomarchy";
+    enable = lib.mkDefault true;
+    wayland.enable = lib.mkDefault true;
+    theme = lib.mkDefault "nomarchy";
   };
 
   services.displayManager.defaultSession = lib.mkDefault "hyprland-uwsm";
@@ -32,12 +32,12 @@ in
     user = lib.mkDefault "nomarchy";
   };
 
-  environment.systemPackages = [ nomarchy-sddm-theme ];
+  environment.systemPackages = lib.mkDefault [ nomarchy-sddm-theme ];
 
   # Enable Hyprland system-level dependencies
   programs.hyprland = {
-    enable = true;
-    withUWSM = true;
+    enable = lib.mkDefault true;
+    withUWSM = lib.mkDefault true;
   };
-  programs.uwsm.enable = true;
+  programs.uwsm.enable = lib.mkDefault true;
 }