Implement risk checks: cooldown, hourly limit, and daily drawdown

Implemented 3 critical risk checks in /api/trading/check-risk:

1. Daily Drawdown Check
   - Blocks trades if today's P&L < maxDailyDrawdown
   - Prevents catastrophic daily losses
   - Currently: -0 limit (configurable via MAX_DAILY_DRAWDOWN)

2. Hourly Trade Limit
   - Blocks trades if tradesInLastHour >= maxTradesPerHour
   - Prevents overtrading / algorithm malfunction
   - Currently: 20 trades/hour (configurable via MAX_TRADES_PER_HOUR)

3. Cooldown Period
   - Blocks trades if timeSinceLastTrade < minTimeBetweenTrades
   - Enforces breathing room between trades
   - Uses minutes (not seconds) thanks to previous commit
   - Currently: 0 min = disabled (configurable via MIN_TIME_BETWEEN_TRADES)

Added database helper functions:
- getLastTradeTime() - Returns timestamp of most recent trade
- getTradesInLastHour() - Counts trades in last 60 minutes
- getTodayPnL() - Sums realized P&L since midnight

All checks include detailed logging with values and thresholds.
Risk check called by n8n workflow before every trade execution.

lib/database/trades.ts

@@ -251,6 +251,78 @@ export async function getOpenTrades() {
   }
 }
 
+/**
+ * Get the most recent trade entry time (for cooldown checking)
+ */
+export async function getLastTradeTime(): Promise<Date | null> {
+  const prisma = getPrismaClient()
+  
+  try {
+    const lastTrade = await prisma.trade.findFirst({
+      orderBy: { entryTime: 'desc' },
+      select: { entryTime: true },
+    })
+    
+    return lastTrade?.entryTime || null
+  } catch (error) {
+    console.error('❌ Failed to get last trade time:', error)
+    return null
+  }
+}
+
+/**
+ * Get count of trades in the last hour
+ */
+export async function getTradesInLastHour(): Promise<number> {
+  const prisma = getPrismaClient()
+  
+  try {
+    const oneHourAgo = new Date(Date.now() - 60 * 60 * 1000)
+    
+    const count = await prisma.trade.count({
+      where: {
+        entryTime: {
+          gte: oneHourAgo,
+        },
+      },
+    })
+    
+    return count
+  } catch (error) {
+    console.error('❌ Failed to get trades in last hour:', error)
+    return 0
+  }
+}
+
+/**
+ * Get total P&L for today
+ */
+export async function getTodayPnL(): Promise<number> {
+  const prisma = getPrismaClient()
+  
+  try {
+    const startOfDay = new Date()
+    startOfDay.setHours(0, 0, 0, 0)
+    
+    const result = await prisma.trade.aggregate({
+      where: {
+        entryTime: {
+          gte: startOfDay,
+        },
+        status: 'closed',
+      },
+      _sum: {
+        realizedPnL: true,
+      },
+    })
+    
+    return result._sum.realizedPnL || 0
+  } catch (error) {
+    console.error('❌ Failed to get today PnL:', error)
+    return 0
+  }
+}
+
 /**
  * Add price update for a trade (for tracking max gain/drawdown)
  */