feat: add loading spinners on tab switch for data-driven tabs

Show a CSS spinner overlay when switching to Autonomous Stats (tab6),
Memories (tab9), and DM Management (tab10). Spinner only shows on
first visit when content is empty, removed after data loads.

bot/static/index.html

@@ -455,6 +455,28 @@
     .tab-content.active {
       display: block;
     }
+
+    /* Tab loading spinner */
+    .tab-loading-overlay {
+      display: flex;
+      align-items: center;
+      justify-content: center;
+      padding: 3rem 1rem;
+      color: #888;
+      font-size: 1rem;
+      gap: 0.75rem;
+    }
+    .tab-loading-overlay .spinner {
+      width: 24px;
+      height: 24px;
+      border: 3px solid #444;
+      border-top-color: #4CAF50;
+      border-radius: 50%;
+      animation: spin 0.8s linear infinite;
+    }
+    @keyframes spin {
+      to { transform: rotate(360deg); }
+    }
     
     /* Chat Interface Styles */
     .chat-message {
@@ -1852,16 +1874,43 @@ function switchTab(tabId) {
     loadStatus();
     loadLastPrompt();
   }
+  if (tabId === 'tab6') {
+    showTabLoading('tab6');
+    loadAutonomousStats().finally(() => hideTabLoading('tab6'));
+  }
   if (tabId === 'tab9') {
     console.log('🧠 Refreshing memory stats for Memories tab');
-    refreshMemoryStats();
+    showTabLoading('tab9');
+    refreshMemoryStats().finally(() => hideTabLoading('tab9'));
   }
   if (tabId === 'tab10') {
     console.log('📱 Loading DM users for DM Management tab');
-    loadDMUsers();
+    showTabLoading('tab10');
+    loadDMUsers().finally(() => hideTabLoading('tab10'));
   }
 }
 
+function showTabLoading(tabId) {
+  const tab = document.getElementById(tabId);
+  if (!tab) return;
+  // Only show if no data loaded yet (first visit)
+  if (tab.querySelector('.tab-loading-overlay')) return;
+  const sections = tab.querySelectorAll('.section');
+  const hasContent = Array.from(sections).some(s => s.querySelector('[id]')?.innerHTML?.trim());
+  if (hasContent) return; // Data already loaded, skip spinner
+  const overlay = document.createElement('div');
+  overlay.className = 'tab-loading-overlay';
+  overlay.innerHTML = '<div class="spinner"></div> Loading...';
+  tab.prepend(overlay);
+}
+
+function hideTabLoading(tabId) {
+  const tab = document.getElementById(tabId);
+  if (!tab) return;
+  const overlay = tab.querySelector('.tab-loading-overlay');
+  if (overlay) overlay.remove();
+}
+
 // ============================================================================
 // Initialization — all setup in one DOMContentLoaded
 // ============================================================================