Improve indicators panel and fix data collector startup

Dashboard:
- Add indicator checkboxes with multi-select support
- Show color dots for each plot group in indicator list
- Config panel always visible with helpful empty state message
- Support multi-color indicators (HTS shows Fast/Slow colors)
- Add line type selector (solid/dotted/dashed) and line width
- Combine SMA/EMA into unified MA indicator with type selector

Data Collector:
- Fix missing asyncio import in database.py (caused NameError on timeout)
- Add startup backfill for all standard intervals on collector restart
- Add gap detection + time-based backfill for robustness
- Add backfill_gap.py tool for manual gap filling
- Optimize custom timeframe generation to only generate missing candles (not all from beginning)

Files changed:
- src/api/dashboard/static/js/ui/indicators-panel.js
- src/api/dashboard/static/js/indicators/index.js, ma_indicator.js
- src/api/dashboard/static/js/strategies/config.js
- src/api/dashboard/static/js/ui/chart.js
- src/api/dashboard/static/js/app.js
- src/api/dashboard/static/index.html
- src/data_collector/database.py
- src/data_collector/main.py
- src/data_collector/custom_timeframe_generator.py
- src/data_collector/backfill_gap.py (new)

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

@@ -1,8 +1,7 @@
 export { MA } from './ma.js';
 export { BaseIndicator } from './base.js';
 export { HTSIndicator } from './hts.js';
-export { SMAIndicator } from './sma.js';
-export { EMAIndicator } from './ema.js';
+export { MAIndicator } from './ma_indicator.js';
 export { RSIIndicator } from './rsi.js';
 export { BollingerBandsIndicator } from './bb.js';
 export { MACDIndicator } from './macd.js';
@@ -10,8 +9,7 @@ export { StochasticIndicator } from './stoch.js';
 export { ATRIndicator } from './atr.js';
 
 import { HTSIndicator } from './hts.js';
-import { SMAIndicator } from './sma.js';
-import { EMAIndicator } from './ema.js';
+import { MAIndicator } from './ma_indicator.js';
 import { RSIIndicator } from './rsi.js';
 import { BollingerBandsIndicator } from './bb.js';
 import { MACDIndicator } from './macd.js';
@@ -20,8 +18,7 @@ import { ATRIndicator } from './atr.js';
 
 export const IndicatorRegistry = {
     hts: HTSIndicator,
-    sma: SMAIndicator,
-    ema: EMAIndicator,
+    ma: MAIndicator,
     rsi: RSIIndicator,
     bb: BollingerBandsIndicator,
     macd: MACDIndicator,