Refine strategy simulation with pyramiding, partial exits, and fixed marker logic

- Implement position pyramiding and 15% partial profit-taking
- Add mutual exclusion between entry and exit in the same candle
- Optimize simulation to use cached indicator results
- Revert Hurst Bands signal logic to cross-down (dip entry)
- Add safety filter for chart markers to prevent rendering errors

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

@@ -604,10 +604,14 @@ async loadSignals() {
         // Merge simulation markers if present
         if (this.simulationMarkers && this.simulationMarkers.length > 0) {
             markers = [...markers, ...this.simulationMarkers];
-            // Re-sort combined markers by time
-            markers.sort((a, b) => a.time - b.time);
         }
         
+        // CRITICAL: Filter out any markers with invalid timestamps before passing to chart
+        markers = markers.filter(m => m && m.time !== null && m.time !== undefined && !isNaN(m.time));
+        
+        // Re-sort combined markers by time
+        markers.sort((a, b) => a.time - b.time);
+        
         // If we have a marker controller, update markers through it
         if (this.markerController) {
             try {