Fix dashboard loading and maximize chart area

- Fixed TA panel loading state - now waits for initial data before loading technical analysis
- Changed initial loading message from 'Loading technical analysis...' to 'Waiting for candle data...'
- Made strategy simulation sidebar collapsed by default to maximize chart area
- Added refresh timestamp to TA panel when manually refreshed
- Improved error messages for when data isn't available in database

src/api/dashboard/static/js/ui/sidebar.js

@@ -16,8 +16,9 @@ export function toggleSidebar() {
 }
 
 export function restoreSidebarState() {
-    const collapsed = localStorage.getItem('sidebar_collapsed') === 'true';
-    if (collapsed) {
-        document.getElementById('rightSidebar').classList.add('collapsed');
+    const collapsed = localStorage.getItem('sidebar_collapsed') !== 'false'; // Default to collapsed
+    const sidebar = document.getElementById('rightSidebar');
+    if (collapsed && sidebar) {
+        sidebar.classList.add('collapsed');
     }
 }