feat: Feature 1.3 — Prop Analysis Engine with 6-step grading pipeline

Core intelligence for BetonBLK prop analysis:
- POST /api/analyze/prop — single prop analysis
- POST /api/analyze/batch — multi-prop analysis for parlay scanner
- 6-step pipeline: season avg → recent form → situational splits →
  cross-book lines → kill conditions → grade (A/B/C/D)
- 6 kill conditions: low_minutes, small_sample, b2b_high_usage,
  blowout_risk, split_conflict, no_opponent_data
- Composite scoring with confidence (30-95), bonuses, penalties
- Added spreads market to Odds API fetch (zero extra credits)
- Full reasoning output with step-by-step breakdown

36 new tests (unit + integration), 128 total across all features

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

src/services/oddsService.js

@@ -1,11 +1,11 @@
 const axios = require('axios');
 const { getRedisClient } = require('../utils/redis');
-const { normalizeProps, MARKET_MAP } = require('../utils/oddsNormalizer');
+const { normalizeProps, extractSpreads, MARKET_MAP } = require('../utils/oddsNormalizer');
 
 const ODDS_API_BASE = 'https://api.the-odds-api.com/v4/sports';
 const CACHE_TTL = 900; // 15 minutes in seconds
 const SPORT_KEYS = { nba: 'basketball_nba', ncaab: 'basketball_ncaab' };
-const ALL_MARKETS = Object.keys(MARKET_MAP).join(',');
+const ALL_MARKETS = Object.keys(MARKET_MAP).join(',') + ',spreads';
 const BOOKMAKERS = 'draftkings,fanduel,betmgm';
 
 function getCacheKey(sport) {
@@ -91,11 +91,12 @@ async function fetchAllOdds(sport, apiKey) {
   }
 
   const props = normalizeProps(eventsWithOdds);
+  const spreads = extractSpreads(eventsWithOdds);
   const quotaRemaining = lastHeaders['x-requests-remaining']
     ? parseInt(lastHeaders['x-requests-remaining'], 10)
     : null;
 
-  return { props, quotaRemaining, headers: lastHeaders };
+  return { props, spreads, quotaRemaining, headers: lastHeaders };
 }
 
 function parseQuota(headers) {
@@ -119,6 +120,7 @@ async function getOdds(sport) {
       source: 'cache',
       quota_remaining: quota,
       props: data.props,
+      spreads: data.spreads || [],
     };
   }
 
@@ -132,7 +134,7 @@ async function getOdds(sport) {
 
   // Fetch live data
   try {
-    const { props, quotaRemaining, headers } = await fetchAllOdds(sport, apiKey);
+    const { props, spreads, quotaRemaining, headers } = await fetchAllOdds(sport, apiKey);
 
     // Update quota in Redis
     if (headers) {
@@ -140,7 +142,7 @@ async function getOdds(sport) {
     }
 
     const now = new Date().toISOString();
-    const cacheData = { updated_at: now, props };
+    const cacheData = { updated_at: now, props, spreads };
     await redis.set(cacheKey, JSON.stringify(cacheData), 'EX', CACHE_TTL);
 
     return {
@@ -149,6 +151,7 @@ async function getOdds(sport) {
       source: 'live',
       quota_remaining: quotaRemaining,
       props,
+      spreads,
     };
   } catch (err) {
     // If API fails, try stale cache (no TTL check — any cached data)
@@ -163,6 +166,7 @@ async function getOdds(sport) {
         stale: true,
         quota_remaining: quota,
         props: data.props,
+        spreads: data.spreads || [],
       };
     }