Implement Strategy tab with Ping-Pong backtesting and crossover-based signal logic

- Add 'Strategy' tab to sidebar for backtesting simulations
- Create strategy-panel.js for Ping-Pong and Accumulation mode simulations
- Refactor all indicators (MA, HTS, RSI, MACD, BB, STOCH, Hurst) to use strict crossover-based signal calculation
- Update chart.js with setSimulationMarkers and clearSimulationMarkers support
- Implement single-entry rule in Ping-Pong simulation mode

src/api/dashboard/static/js/indicators/stoch.js

@@ -32,33 +32,38 @@ class BaseIndicator {
 }
 
 // Signal calculation for Stochastic
-function calculateStochSignal(indicator, lastCandle, prevCandle, values) {
+function calculateStochSignal(indicator, lastCandle, prevCandle, values, prevValues) {
     const k = values?.k;
     const d = values?.d;
+    const prevK = prevValues?.k;
+    const prevD = prevValues?.d;
     const overbought = indicator.params?.overbought || 80;
     const oversold = indicator.params?.oversold || 20;
     
-    if (!k || !d) {
+    if (k === undefined || d === undefined || prevK === undefined || prevD === undefined) {
         return null;
     }
 
-    if (k < oversold && d < oversold) {
+    // BUY: %K crosses UP through %D while both are oversold
+    if (prevK <= prevD && k > d && k < oversold) {
         return {
             type: SIGNAL_TYPES.BUY,
-            strength: Math.min(50 + (oversold - k) * 2, 100),
+            strength: 80,
             value: k,
-            reasoning: `Stochastic %K (${k.toFixed(2)}) and %D (${d.toFixed(2)}) oversold (<${oversold})`
+            reasoning: `Stochastic %K crossed UP through %D in oversold zone`
         };
-    } else if (k > overbought && d > overbought) {
+    } 
+    // SELL: %K crosses DOWN through %D while both are overbought
+    else if (prevK >= prevD && k < d && k > overbought) {
         return {
             type: SIGNAL_TYPES.SELL,
-            strength: Math.min(50 + (k - overbought) * 2, 100),
+            strength: 80,
             value: k,
-            reasoning: `Stochastic %K (${k.toFixed(2)}) and %D (${d.toFixed(2)}) overbought (>${overbought})`
+            reasoning: `Stochastic %K crossed DOWN through %D in overbought zone`
         };
-    } else {
-        return null;
     }
+
+    return null;
 }
 
 // Stochastic Oscillator Indicator class