Fix update button persistence with more robust implementation

- Completely redesigned update notification system with dedicated functions
- Added showUpdateAlert and hideUpdateAlert functions for better control
- Improved update status persistence with namespaced localStorage keys
- Added custom CSS styles with \!important to prevent style overrides
- Modified toggle test functionality to directly show/hide the update alert
- Prevented update notifications from being cleared on errors
- Added forced display styles and higher z-index for visibility
- Added debugging logs to verify update detection

🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

public/index.html

@@ -137,8 +137,8 @@
                                             <div class="mt-2 testing-controls">
                                                 <small><a href="#" id="toggle-test-update-button">Toggle Test Update</a></small>
                                             </div>
-                                            <div id="update-available" class="mt-3 d-none">
-                                                <div class="alert alert-info">
+                                            <div id="update-available" class="mt-3">
+                                                <div class="alert alert-info update-alert" style="display: none;">
                                                     <i class="fas fa-arrow-circle-up"></i> 
                                                     <span>A new version is available!</span>
                                                     <button id="btn-update-now" class="btn btn-sm btn-primary ml-2">
@@ -669,6 +669,26 @@
         </div>
     </div>
 
+    <!-- Update Alert Custom Styles -->
+    <style>
+        /* Custom styles for update alert to ensure it's visible */
+        .update-alert {
+            display: none;
+            margin-top: 10px !important;
+            border: 2px solid #007bff !important;
+            background-color: #cce5ff !important;
+            color: #004085 !important;
+            font-weight: bold !important;
+            box-shadow: 0 2px 5px rgba(0,0,0,0.2) !important;
+            position: relative !important;
+            z-index: 100 !important;
+        }
+        .update-alert span {
+            color: #004085 !important;
+            font-weight: bold !important;
+        }
+    </style>
+    
     <!-- JavaScript Files -->
     <script src="/js/system-status.js"></script>
     <script src="/js/app.js"></script>