Refactor dashboard JS to ES modules; fix collector strategy loading and add auto-backfill

- Split inline JS into separate ES module files (indicators/, strategies/, ui/, utils/)
- Fix brain.py strategy registry to use MAStrategy directly instead of missing modules
- Add auto-backfill for detected data gaps in collector monitoring loop
- Fix chart resize on sidebar toggle
- Fix chart scrollToTime -> setVisibleLogicalRange

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

@@ -0,0 +1,36 @@
+import { BaseIndicator } from './base.js';
+
+export class ATRIndicator extends BaseIndicator {
+    calculate(candles) {
+        const period = this.params.period || 14;
+        const results = new Array(candles.length).fill(null);
+        const tr = new Array(candles.length).fill(0);
+        
+        for (let i = 1; i < candles.length; i++) {
+            const h_l = candles[i].high - candles[i].low;
+            const h_pc = Math.abs(candles[i].high - candles[i-1].close);
+            const l_pc = Math.abs(candles[i].low - candles[i-1].close);
+            tr[i] = Math.max(h_l, h_pc, l_pc);
+        }
+        
+        let atr = 0;
+        let sum = 0;
+        for (let i = 1; i <= period; i++) sum += tr[i];
+        atr = sum / period;
+        results[period] = atr;
+        
+        for (let i = period + 1; i < candles.length; i++) {
+            atr = (atr * (period - 1) + tr[i]) / period;
+            results[i] = atr;
+        }
+        return results;
+    }
+    
+    getMetadata() {
+        return {
+            name: 'ATR',
+            inputs: [{ name: 'period', label: 'Period', type: 'number', default: 14, min: 1, max: 100 }],
+            plots: [{ id: 'value', color: '#795548', title: 'ATR' }]
+        };
+    }
+}