🐛 Fix Alpine.js SyntaxError and backlink visibility issues

- Fix SyntaxError in viewer.js line 2868 (.bind(this) issue in setTimeout)
- Resolve Alpine.js 'Can't find variable' errors (documentViewer, goBack, etc.)
- Fix backlink rendering and persistence during temporary highlights
- Add backlink protection and restoration mechanism in highlightAndScrollToText
- Implement Note Management System with hierarchical notebooks
- Add note highlights and memos functionality
- Update cache version to force browser refresh (v=2025012641)
- Add comprehensive logging for debugging backlink issues

frontend/index.html

@@ -88,6 +88,11 @@
                                         class="px-3 py-2 rounded-md">
                                     <i class="fas fa-list mr-2"></i>목차
                                 </button>
+                                
+                                <button onclick="window.location.href='/notes.html'" 
+                                        class="px-3 py-2 rounded-md bg-green-600 text-white hover:bg-green-700 transition-colors">
+                                    <i class="fas fa-sticky-note mr-2"></i>노트
+                                </button>
                             </div>
                         </div>
                         
@@ -487,6 +492,6 @@
     <!-- JavaScript 파일들 -->
     <script src="/static/js/api.js?v=2025012380"></script>
     <script src="/static/js/auth.js?v=2025012351"></script>
-    <script src="/static/js/main.js?v=2025012374"></script>
+    <script src="/static/js/main.js?v=2025012462"></script>
 </body>
 </html>