feat: Feature 1.5 — Bet Submission with 3 methods + performance tracking

Three submission methods:
- POST /api/bets/quickslip — structured bet entry
- POST /api/bets/screenshot — stub OCR with confirm flow
- POST /api/bets/sync — coming soon stub

Full bet lifecycle:
- PATCH /api/bets/:id/settle — settle with outcome, recalculates performance
- GET /api/bets — list with status/book/pagination filters
- GET /api/bets/performance — ROI, win rate, profit (weekly/monthly/all_time)

Payout calculator handles straight bets (American odds) and parlays
(multiplied leg payouts). Performance service recalculates on each
settlement and upserts into performance table.

33 new tests, 221 total (194 Node.js + 27 Python), all passing.
All backend features for Phase 1 + Phase 2 now complete.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/services/payoutCalculator.js

@@ -0,0 +1,31 @@
+function calculateStraightPayout(amount, odds) {
+  if (odds < 0) {
+    return amount + (amount / (Math.abs(odds) / 100));
+  }
+  return amount + (amount * (odds / 100));
+}
+
+function calculateParlayPayout(amount, legsOdds) {
+  let multiplier = 1;
+  for (const odds of legsOdds) {
+    if (odds < 0) {
+      multiplier *= 1 + (100 / Math.abs(odds));
+    } else {
+      multiplier *= 1 + (odds / 100);
+    }
+  }
+  return amount * multiplier;
+}
+
+function calculatePayout(amount, betType, legsOdds) {
+  if (!legsOdds || legsOdds.length === 0) return amount;
+
+  if (betType === 'straight' || legsOdds.length === 1) {
+    return Math.round(calculateStraightPayout(amount, legsOdds[0]) * 100) / 100;
+  }
+
+  // parlay, teaser, round_robin all use multiplied odds for MVP
+  return Math.round(calculateParlayPayout(amount, legsOdds) * 100) / 100;
+}
+
+module.exports = { calculatePayout, calculateStraightPayout, calculateParlayPayout };