Issue 1: Only update lastSignalDate when signal type changes (BUY→SELL or SELL→BUY)
- Modified clearIndicatorCaches() to accept clearSignalState parameter
- When new candle completes: only clear cachedResults/cachedMeta (not signal state)
- When timeframe changes: clear everything including signal tracking
- This preserves signal change history across multiple candles
Issue 2: Indicator lines not updating when new candles arrive
- Added updateIndicatorCandles() function to update existing series
- Instead of removing and recreating series, now uses .setData() to update
- Called when new candle is detected to update indicator lines
- Chart renders correctly with new data after each candle completion
Both issues now resolved:
1. Shows last crossover date only when signal actually changes
2. Indicator lines update in real-time when new candles complete
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