fix: loading indicator now properly hides after blazor initializes

**Issue**: Loading indicator (spinner) continues to display even after page fully loads

**Root cause**:
- Blazor.start() was already called by blazor.web.js (auto-starts)
- Calling it again in JavaScript won't trigger promise resolution
- Promise callback never executed, overlay never hidden

**Solution**: Use multiple detection methods to ensure loading hides:
1. Blazor 'ready' event listener (when circuit is ready)
2. DOMContentLoaded + 500ms timeout (fallback)
3. MutationObserver watching for 20+ MudBlazor components

**Result**:
- Loading spinner shows: page load starts
- Spinner hides: when ANY of the above conditions met (whichever is first)
- No more stuck loading indicator

This ensures loading always hides regardless of how Blazor initializes.

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

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

@@ -15,16 +15,48 @@ window.taxbaikAdminSession = {
         window.taxbaikAdminSession.syncRouteClass();
         window.addEventListener('popstate', window.taxbaikAdminSession.syncRouteClass);
 
-        // Show loading indicator on page load (hide when Blazor circuit connects)
+        // Show loading indicator on page load, hide when content renders
         const loadingOverlay = document.getElementById('blazor-loading');
         if (loadingOverlay) {
-            loadingOverlay.classList.add('show');
-            // Hide loading when Blazor is ready
-            Blazor.start().then(() => {
-                if (loadingOverlay) {
-                    loadingOverlay.classList.remove('show');
+            // Hide loading when page is fully interactive
+            // Watch for Blazor components to render
+            const hideLoading = () => {
+                loadingOverlay.classList.remove('show');
+                document.removeEventListener('blazor:ready', hideLoading);
+                observer.disconnect();
+            };
+
+            // Hide on Blazor ready event
+            document.addEventListener('blazor:ready', hideLoading);
+
+            // Also hide after DOM content loaded + small delay
+            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')) {
+                    hideLoading();
                 }
             });
+            observer.observe(document.body, {
+                childList: true,
+                subtree: true
+            });
         }
 
         const modal = document.getElementById('components-reconnect-modal');