feat: implement robust browser process cleanup system

- Add cleanup-chromium.sh script for manual zombie process cleanup
- Add docker-entrypoint.sh with signal handlers for graceful shutdown
- Add lib/process-cleanup.ts for automatic cleanup on app termination
- Enhanced forceCleanup() method in tradingview-automation.ts:
  - Individual page closing before browser termination
  - Force kill remaining processes with SIGKILL
  - Reset operation locks after cleanup
- Improved browser launch args to prevent zombie processes:
  - Better crash reporter handling
  - Enhanced background process management
  - Removed problematic --single-process flag
- Updated Dockerfile to use new entrypoint with cleanup handlers
- Set DOCKER_ENV environment variable for container detection
- Add proper signal handling (SIGINT, SIGTERM, SIGQUIT)
- Automatic cleanup of temporary Puppeteer profiles

Resolves zombie Chromium process accumulation issue

docker-entrypoint.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+
+# Trading Bot Startup Script with Process Cleanup
+# This script initializes the process cleanup handlers and starts the Next.js app
+
+echo "🚀 Starting Trading Bot with Process Cleanup..."
+
+# Initialize process cleanup
+echo "🧹 Initializing process cleanup handlers..."
+
+# Create a signal handler to cleanup on container stop
+cleanup() {
+    echo "🛑 Received shutdown signal, cleaning up..."
+    
+    # Kill any remaining chromium processes
+    pkill -f "chromium" 2>/dev/null || true
+    
+    # Clean up temporary files
+    rm -rf /tmp/puppeteer_dev_chrome_profile-* 2>/dev/null || true
+    
+    echo "✅ Cleanup completed"
+    exit 0
+}
+
+# Register signal handlers
+trap cleanup SIGINT SIGTERM SIGQUIT
+
+# Start the Next.js application
+echo "🚀 Starting Next.js application..."
+if [ "$NODE_ENV" = "development" ]; then
+    exec npm run dev:docker
+else
+    exec npm start
+fi