fix: move comfyui-theme.css to lib/tailwind/ for proper serving

The Python API only has static file routes for /prompt_manager/lib/
and /prompt_manager/js/ — no route exists for /css/. The theme CSS
was returning 404, causing all --pm-* variables to be undefined
(white/transparent rendering). Moved to lib/tailwind/ where the
existing route serves it correctly.

web/admin.html

@@ -5,7 +5,7 @@
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>PromptManager - Admin Dashboard</title>
     <script src="/prompt_manager/js/theme-bridge.js"></script>
-    <link rel="stylesheet" href="css/comfyui-theme.css">
+    <link rel="stylesheet" href="lib/tailwind/comfyui-theme.css">
     <link rel="stylesheet" href="lib/tailwind/styles.css">
     <link rel="stylesheet" href="lib/viewerjs/viewer.min.css">
     <script src="lib/viewerjs/viewer.min.js"></script>

web/gallery.html

@@ -5,7 +5,7 @@
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>PromptManager - Gallery</title>
     <script src="/prompt_manager/js/theme-bridge.js"></script>
-    <link rel="stylesheet" href="css/comfyui-theme.css">
+    <link rel="stylesheet" href="lib/tailwind/comfyui-theme.css">
     <link rel="stylesheet" href="lib/tailwind/styles.css">
     <link rel="stylesheet" href="lib/viewerjs/viewer.min.css">
     <script src="lib/viewerjs/viewer.min.js"></script>

web/metadata.html

@@ -5,7 +5,7 @@
     <meta name="viewport" content="width=device-width, initial-scale=1.0">
     <title>Image Gallery - Generation Data</title>
     <script src="/prompt_manager/js/theme-bridge.js"></script>
-    <link rel="stylesheet" href="css/comfyui-theme.css">
+    <link rel="stylesheet" href="lib/tailwind/comfyui-theme.css">
     <link rel="stylesheet" href="lib/tailwind/styles.css">
     <style>
         /* Ensure the layout takes full height and prevents overflow */