feat: Replace blind 2-hour reconnect with error-based health monitoring

User Request: Replace blind 2-hour restart timer with smart monitoring that only restarts when accountUnsubscribe errors actually occur

Changes:
. Health Monitor (NEW):
- Created lib/monitoring/drift-health-monitor.ts
- Tracks accountUnsubscribe errors in 30-second sliding window
- Triggers container restart via flag file when 50+ errors detected
- Prevents unnecessary restarts when SDK healthy

. Drift Client:
- Removed blind scheduleReconnection() and 2-hour timer
- Added interceptWebSocketErrors() to catch SDK errors
- Patches console.error to monitor for accountUnsubscribe patterns
- Starts health monitor after successful initialization
- Removed unused reconnect() method and reconnectTimer field

. Health API (NEW):
- GET /api/drift/health - Check current error count and health status
- Returns: healthy boolean, errorCount, threshold, message
- Useful for external monitoring and debugging

Impact:
- System only restarts when actual memory leak detected
- Prevents unnecessary downtime every 2 hours
- More targeted response to SDK issues
- Better operational stability

Files:
- lib/monitoring/drift-health-monitor.ts (NEW - 165 lines)
- lib/drift/client.ts (removed timer, added error interception)
- app/api/drift/health/route.ts (NEW - health check endpoint)

Testing:
- Health monitor starts on initialization: ✅
- API endpoint returns healthy status: ✅
- No blind reconnection scheduled: ✅

app/api/drift/health/route.ts

@@ -0,0 +1,29 @@
+/**
+ * Drift Health Check API
+ * 
+ * GET /api/drift/health - Get current health status
+ */
+
+import { NextRequest, NextResponse } from 'next/server'
+import { getDriftHealthMonitor } from '@/lib/monitoring/drift-health-monitor'
+
+export async function GET(req: NextRequest) {
+  try {
+    const monitor = getDriftHealthMonitor()
+    const status = monitor.getHealthStatus()
+    
+    return NextResponse.json({
+      success: true,
+      ...status,
+      message: status.healthy 
+        ? 'Drift SDK connections healthy' 
+        : `Warning: ${status.errorCount} accountUnsubscribe errors detected`
+    })
+    
+  } catch (error: any) {
+    return NextResponse.json({
+      success: false,
+      error: error.message
+    }, { status: 500 })
+  }
+}