feat: OAuth user fixes + dashboard UI improvements (v3.2.0)

- Bug A: Fix OAuth consent redirect loop (return_url path-relative)
- Bug B: Accept OAuth JWT tokens on /u/{user_id}/{alias}/mcp
- Bug C: Add user OAuth client CRUD (list/create/delete) + new page
- D-1: Sidebar border via Tailwind class, version footer in sidebar
- D-2: Remove broken setInterval targeting #stats-container
- D-3: 404.html purple primary colors + system dark mode support
- D-4: Fix invisible buttons (bg-gray-200 + text-white in light mode)
- D-5: Pin Alpine.js to 3.14.8, remove duplicate CSRF meta tag
- D-6: Fix invisible lang toggle button in settings (dark mode)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

core/templates/dashboard/base.html

@@ -102,9 +102,8 @@
       })">
     <div class="flex h-screen overflow-hidden">
         <!-- Sidebar -->
-        <aside class="sidebar-transition bg-white dark:bg-gray-800 border-gray-200 dark:border-gray-700 flex flex-col"
-            :class="sidebarOpen ? 'w-64' : 'w-20'" {% if lang=='fa' %}style="border-left: 1px solid;" {% else
-            %}style="border-right: 1px solid;" {% endif %}>
+        <aside class="sidebar-transition bg-white dark:bg-gray-800 border-gray-200 dark:border-gray-700 flex flex-col {% if lang=='fa' %}border-l{% else %}border-r{% endif %} border-gray-200 dark:border-gray-700"
+            :class="sidebarOpen ? 'w-64' : 'w-20'">
             <!-- Logo -->
             <div class="flex items-center justify-between h-16 px-4 border-b border-gray-200 dark:border-gray-700">
                 <div class="flex items-center" x-show="sidebarOpen">
@@ -207,6 +206,11 @@
                 {% endif %}
             </nav>
 
+            <!-- Version footer -->
+            <div x-show="sidebarOpen" class="px-4 py-2 text-xs text-gray-400 dark:text-gray-600">
+                v{{ project_version | default('') }}
+            </div>
+
             <!-- User Section -->
             <div class="p-4 border-t border-gray-200 dark:border-gray-700">
                 {# Profile link for OAuth users #}