Add Omarchy-style Hyprland desktop for straylight

Ports the classic dotfiles Omarchy setup to a no-home-manager NixOS
system module (configs/omarchy.nix), scoped to straylight only so the
other desktop hosts keep i3.

- Hyprland (programs.hyprland) becomes the default lightdm session; i3
  stays enabled and selectable as a fallback.
- Omarchy config layout under ~/.config/{hypr,waybar,rofi,wlogout,
  swayosd,alacritty} symlinked from the store; mutable theme/wallpaper
  state in ~/.config/omarchy/current.
- omarchy-dots generates 8 themes (hyprland/hyprlock/waybar/rofi/
  swayosd/wlogout/alacritty/mako colour files) from each theme's
  palette, with wallpapers fetched from the Omarchy v3.8.4 tag.
- Helper scripts: omarchy-theme-set/bg-next/bg-set/apply, omarchy-menu
  (rofi power/theme/background menus), waybar toggle, screenshot, lock.
- Shared desktop modules (desktop.nix / desktop-light.nix) untouched.

configs/omarchy/hypr/hyprlock.conf

@@ -0,0 +1,44 @@
+# hyprlock — Omarchy v3 config/hypr/hyprlock.conf.
+source = ~/.config/omarchy/current/theme/hyprlock.conf
+
+general {
+    ignore_empty_input = true
+}
+
+background {
+    monitor =
+    color = $color
+    path = ~/.config/omarchy/current/background
+    blur_passes = 3
+}
+
+animations {
+    enabled = false
+}
+
+input-field {
+    monitor =
+    size = 650, 100
+    position = 0, 0
+    halign = center
+    valign = center
+
+    inner_color = $inner_color
+    outer_color = $outer_color
+    outline_thickness = 4
+
+    font_family = JetBrainsMono Nerd Font
+    font_color = $font_color
+
+    placeholder_text = Enter Password
+    check_color = $check_color
+    fail_text = <i>$FAIL ($ATTEMPTS)</i>
+
+    rounding = 0
+    shadow_passes = 0
+    fade_on_empty = false
+}
+
+auth {
+    fingerprint:enabled = false
+}