Add SQL script to fix SHORT position P&L in database

Corrects all historical SHORT trades affected by the P&L calculation bug.

Results:
- 44 SHORT trades corrected
- Total P&L improved from -$388.82 to -$72.98 (+$315.84 recovered)
- SHORT win rate revealed to be 60.5% (not 39% as incorrectly shown)

Script creates backup table before making changes and includes rollback instructions.

scripts/fix_short_pnl.sql

@@ -0,0 +1,93 @@
+-- Fix SHORT position P&L calculation bug in database
+-- 
+-- All SHORT trades have inverted P&L due to calculation bug in closePosition()
+-- This script recalculates the correct P&L for all completed SHORT trades
+
+BEGIN;
+
+-- Create backup table first
+CREATE TABLE IF NOT EXISTS "Trade_backup_20251107" AS 
+SELECT * FROM "Trade";
+
+-- Show current SHORT trade P&L before fix
+SELECT 
+  'BEFORE FIX - SHORT Trades' as status,
+  COUNT(*) as total_shorts,
+  ROUND(SUM("realizedPnL")::numeric, 2) as total_pnl,
+  ROUND(AVG("realizedPnL")::numeric, 2) as avg_pnl
+FROM "Trade"
+WHERE direction = 'short' 
+  AND "exitReason" IS NOT NULL
+  AND "exitReason" NOT LIKE '%CLEANUP%';
+
+-- Update SHORT trades with corrected P&L
+-- Formula: 
+--   priceDiff = entryPrice - exitPrice (profit when price falls)
+--   profitPercent = (priceDiff / entryPrice) * 100
+--   leverage = default 10x (stored in most trades)
+--   collateral = positionSizeUSD / leverage
+--   realizedPnL = collateral * (profitPercent / 100) * leverage
+--   Simplifies to: realizedPnL = positionSizeUSD * (profitPercent / 100)
+
+UPDATE "Trade"
+SET "realizedPnL" = (
+  -- Calculate correct P&L for SHORT positions
+  "positionSizeUSD" * 
+  (("entryPrice" - "exitPrice") / "entryPrice") -- Price diff / entry = profit %
+)
+WHERE direction = 'short' 
+  AND "exitReason" IS NOT NULL
+  AND "exitReason" NOT LIKE '%CLEANUP%'
+  AND "exitPrice" IS NOT NULL
+  AND "entryPrice" > 0;
+
+-- Show corrected SHORT trade P&L after fix
+SELECT 
+  'AFTER FIX - SHORT Trades' as status,
+  COUNT(*) as total_shorts,
+  ROUND(SUM("realizedPnL")::numeric, 2) as total_pnl,
+  ROUND(AVG("realizedPnL")::numeric, 2) as avg_pnl
+FROM "Trade"
+WHERE direction = 'short' 
+  AND "exitReason" IS NOT NULL
+  AND "exitReason" NOT LIKE '%CLEANUP%';
+
+-- Show sample of corrected trades
+SELECT 
+  symbol,
+  direction,
+  ROUND("entryPrice"::numeric, 2) as entry,
+  ROUND("exitPrice"::numeric, 2) as exit,
+  ROUND(("entryPrice" - "exitPrice")::numeric, 2) as price_diff,
+  ROUND((("entryPrice" - "exitPrice") / "entryPrice" * 100)::numeric, 3) as profit_pct,
+  ROUND("realizedPnL"::numeric, 2) as corrected_pnl,
+  "exitReason",
+  "createdAt"
+FROM "Trade"
+WHERE direction = 'short' 
+  AND "exitReason" IS NOT NULL
+  AND "exitReason" NOT LIKE '%CLEANUP%'
+ORDER BY "createdAt" DESC
+LIMIT 10;
+
+-- Show overall stats comparison
+SELECT 
+  direction,
+  COUNT(*) as trades,
+  ROUND(SUM("realizedPnL")::numeric, 2) as total_pnl,
+  ROUND(AVG("realizedPnL")::numeric, 2) as avg_pnl,
+  ROUND(100.0 * SUM(CASE WHEN "realizedPnL" > 0 THEN 1 ELSE 0 END) / COUNT(*)::numeric, 1) as win_rate
+FROM "Trade"
+WHERE "exitReason" IS NOT NULL
+  AND "exitReason" NOT LIKE '%CLEANUP%'
+  AND "isTestTrade" = false
+GROUP BY direction
+ORDER BY direction;
+
+COMMIT;
+
+-- To rollback if something goes wrong:
+-- BEGIN;
+-- DELETE FROM "Trade";
+-- INSERT INTO "Trade" SELECT * FROM "Trade_backup_20251107";
+-- COMMIT;