Restore Unlock screen selection to the Style menu

Bring back per-theme Plymouth unlock theming, dropped when walker +
elephant were removed. Selection now uses the same image carousel as
the theme and background switchers instead of a name list.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

bin/omarchy-plymouth-list

@@ -0,0 +1,19 @@
+#!/bin/bash
+
+# omarchy:summary=List themes that can style the Plymouth boot screen
+# omarchy:examples=omarchy plymouth list
+
+{
+  find ~/.config/omarchy/themes/ -mindepth 1 -maxdepth 1 \( -type d -o -type l \) -printf '%f\n' 2>/dev/null
+  find "$OMARCHY_PATH/themes/" -mindepth 1 -maxdepth 1 -type d -printf '%f\n'
+} | sort -u | while read -r name; do
+  if [[ -d ~/.config/omarchy/themes/$name ]]; then
+    theme_dir=~/.config/omarchy/themes/$name
+  else
+    theme_dir="$OMARCHY_PATH/themes/$name"
+  fi
+
+  if [[ -f $theme_dir/preview-unlock.png ]]; then
+    echo "$name"
+  fi
+done