add backtest report UI to the Track Record tab

New BacktestPanel: shows qualified hit-rate/expectancy vs the all-setups baseline,
a by-direction breakdown, and the probability calibration table (predicted vs
realized, over-confident buckets flagged amber). Includes a "Run backtest" button
that triggers the job and a plain explanation of the method and its limits.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/types.ts

@@ -179,6 +179,36 @@ export interface SentimentProviderConfig {
   custom_base_url_providers: string[];
 }
 
+export interface BacktestBucket {
+  total: number;
+  wins: number;
+  losses: number;
+  expired: number;
+  hit_rate: number | null;
+  avg_r: number | null;
+  total_r: number | null;
+}
+
+export interface BacktestCalibrationRow {
+  bucket: string;
+  n: number;
+  predicted_avg: number;
+  realized_hit_rate: number;
+}
+
+export interface BacktestReport {
+  generated_at: string;
+  tickers: number;
+  candidates: number;
+  qualified: number;
+  params: { step_days: number; horizon_days: number; min_lookback: number };
+  overall_qualified: BacktestBucket;
+  overall_all: BacktestBucket;
+  by_direction: Record<string, BacktestBucket>;
+  calibration: BacktestCalibrationRow[];
+  note: string;
+}
+
 export interface MarketRegime {
   label: 'bullish' | 'bearish' | 'neutral' | 'unknown';
   benchmark?: string;