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/partials/head_assets.html

@@ -11,7 +11,7 @@
 <script src="https://unpkg.com/htmx.org@1.9.10"></script>
 
 <!-- Alpine.js for simple interactions -->
-<script defer src="https://unpkg.com/alpinejs@3.x.x/dist/cdn.min.js"></script>
+<script defer src="https://unpkg.com/alpinejs@3.14.8/dist/cdn.min.js"></script>
 
 <!-- Custom Tailwind Config -->
 <script>
@@ -50,8 +50,6 @@
     }
 </script>
 
-<meta name="csrf-token" content="{{ request.state.csrf_token }}">
-
 <!-- Global CSRF Interceptor -->
 <script>
     document.addEventListener('DOMContentLoaded', () => {