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/index.html

@@ -1343,14 +1343,14 @@
                         </button>
                     </div>
                 </div>
-                <div class="ta-content" id="taContent">
-                    <div class="ta-loading">Loading technical analysis...</div>
+<div class="ta-content" id="taContent">
+                    <div class="ta-loading">Waiting for candle data...</div>
                 </div>
             </div>
         </div>
         
         <!-- Right Sidebar - Strategy Simulation -->
-        <div class="right-sidebar" id="rightSidebar">
+        <div class="right-sidebar collapsed" id="rightSidebar">
             <div class="sidebar-header">
                 <div class="sidebar-title">
                     <span>🎯</span>