feat: add 5 dashboard features — dark mode, trade history, backtests, model insights, alerts

- Dark mode: class-based theme toggle with localStorage persistence and flash prevention
- Trade History (/trades): paginated table, stats cards, equity curve chart with DB API endpoints
- Backtest Viewer (/backtests): log parser for 35 backtest results, sidebar + detail + comparison tabs
- Model Insights: dashboard card + dialog showing feature importance, regime distribution, training history
- Alert/Signal Log (/alerts): signal stats, filterable table with execution tracking
- API: 8 new endpoints with psycopg2 DB connection pool
- Dark mode sweep across books page, about dialog, and all dashboard components
- Architecture docs rewritten with Mermaid diagrams (23 docs)
- README and FEATURES.md rewritten bilingual (Indonesian + English)
- main_live.py: write model_metrics.json on startup and retrain

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backtests/24_final_combined_results/final_combined_20260207_222406.log

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+#24 Final Combined Results (All 3 Winners)
+Generated: 2026-02-07 22:24:06.260094
+Improvements: #19B Skip TL + #20B EC mom<-50 + #22 ATR-Adaptive
+
+  A: 19B+20B+22C (wider): 725 trades, 76.8% WR, $2,076.47, DD: 3.7%, Sharpe: 2.56, PF: 1.63, vs base: $+626.61
+  B: 19B+20B+22D (tight+wide): 739 trades, 80.4% WR, $2,235.03, DD: 3.4%, Sharpe: 2.87, PF: 1.77, vs base: $+785.17
+
+Best: B: 19B+20B+22D (tight+wide)