fix: unify backtest execution and add forward validation candidates

Share point-in-time signals and a cash-funded order ledger across backtests and trading. Correct eligibility, missing-price fills, quality factors, regime inputs, warmup windows, and cash-injection accounting. Add reproducible registered-strategy comparisons and paired forward candidates with a 20% resize band.

Validation: 125 Python tests, 23 web tests, TypeScript/Vite build, 87 strategy causality checks, and real-data target/order/equity parity for 10 strategies.

web/src/server/strategyService.ts

@@ -17,7 +17,7 @@ function ensureCacheDir(): void {
 }
 
 function configHash(config: BacktestConfig): string {
-  const serialized = stableStringify(config);
+  const serialized = stableStringify({ engine: "cash-ledger-pit-v2", config });
   return createHash("md5").update(serialized).digest("hex").slice(0, 12);
 }