Add max_position_size to account configs

- DB migration: ALTER TABLE account_configs ADD COLUMN max_position_size INTEGER NOT NULL DEFAULT 0
- Added max_position_size to AccountConfigRow, createAccountConfig, updateAccountConfig in lib/db.ts
- Added maxPositionSize to AccountConfig type in types.ts (0 = no limit)
- GET /api/firms/[id] now returns maxPositionSize per account
- POST /api/firms/[id]/accounts and PUT /api/account-configs/[id] accept maxPositionSize
- Firm settings page: new Max Contracts column (blank = no limit)
- auto-trade: contracts capped at maxPositionSize when > 0

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/auto-trade.ts

@@ -41,6 +41,7 @@ function mapFirmConfig(firm: FirmWithAccounts): FirmConfig {
             minTradingDays: a.min_trading_days,
             accountSize: a.account_size,
             maxLoss: a.max_loss,
+            maxPositionSize: a.max_position_size,
         })),
     };
 }
@@ -124,7 +125,8 @@ export async function runTrade(action: 'Buy' | 'Sell', symbol: string) {
         const totalProfit = dailyPnL.reduce((sum, d) => sum + d.pnl, 0);
         const target = computeDailyTarget(cfg.profitTarget, cfg.consistency, totalProfit, dailyPnL);
 
-        const contracts = Math.max(1, Math.ceil(target.amount / 1000));
+        const rawContracts = Math.max(1, Math.ceil(target.amount / 1000));
+        const contracts = cfg.maxPositionSize > 0 ? Math.min(rawContracts, cfg.maxPositionSize) : rawContracts;
         const fill = await client.sendOrder(acc.id, contract.name, contracts, action, 'Market');
 
         // Wait briefly for the cash balance WebSocket update to reflect entry commission