fix: guarantee loading indicator hides with 3-second timeout

**Issue**: Loading indicator remained visible, intercepting all user interactions (pointer-events: auto blocks clicks)

**Root cause**: Multiple detection methods insufficient, race condition between JavaScript execution and Blazor initialization

**Solution**: Add guaranteed 3-second timeout + multiple detection methods
- Method 1: 3000ms timeout (guaranteed)
- Method 2: Detect when 10+ MudBlazor components appear
- Method 3: Hide when readystatechange to 'interactive' or 'complete'

**Failsafe**: Even if Blazor never fires events, loading WILL hide after 3 seconds max

**Result**:
- Loading shows: immediate on page load
- Loading hides: within 1-3 seconds (whichever is first)
- User can interact: guaranteed by 3-second timeout at latest

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

TaxBaik.Web/wwwroot/js/admin-session.js

@@ -15,47 +15,37 @@ window.taxbaikAdminSession = {
         window.taxbaikAdminSession.syncRouteClass();
         window.addEventListener('popstate', window.taxbaikAdminSession.syncRouteClass);
 
-        // Show loading indicator on page load, hide when content renders
+        // Hide loading indicator after Blazor initializes
         const loadingOverlay = document.getElementById('blazor-loading');
         if (loadingOverlay) {
-            // Hide loading when page is fully interactive
-            // Watch for Blazor components to render
             const hideLoading = () => {
+                if (loadingOverlay.classList.contains('show')) {
                     loadingOverlay.classList.remove('show');
-                document.removeEventListener('blazor:ready', hideLoading);
+                }
-                observer.disconnect();
             };
 
-            // Hide on Blazor ready event
+            // Method 1: Hide after 3 seconds (guaranteed timeout)
-            document.addEventListener('blazor:ready', hideLoading);
+            setTimeout(hideLoading, 3000);
 
-            // Also hide after DOM content loaded + small delay
+            // Method 2: Hide when Blazor components appear (faster if available)
-            if (document.readyState === 'loading') {
-                document.addEventListener('DOMContentLoaded', () => {
-                    setTimeout(() => {
-                        if (loadingOverlay.classList.contains('show')) {
-                            hideLoading();
-                        }
-                    }, 500);
-                });
-            } else {
-                setTimeout(() => {
-                    if (loadingOverlay.classList.contains('show')) {
-                        hideLoading();
-                    }
-                }, 500);
-            }
-
-            // Watch for interactive elements to appear
             const observer = new MutationObserver(() => {
                 const mudElements = document.querySelectorAll('[class*="mud-"]').length;
-                if (mudElements > 20 && loadingOverlay.classList.contains('show')) {
+                if (mudElements > 10) {
                     hideLoading();
+                    observer.disconnect();
                 }
             });
             observer.observe(document.body, {
                 childList: true,
-                subtree: true
+                subtree: true,
+                attributes: true
+            });
+
+            // Method 3: Hide when page is interactive
+            document.addEventListener('readystatechange', () => {
+                if (document.readyState === 'interactive' || document.readyState === 'complete') {
+                    setTimeout(hideLoading, 500);
+                }
             });
         }