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

lib/process-cleanup.ts

@@ -0,0 +1,74 @@
+// Process cleanup utility for graceful shutdown
+import { enhancedScreenshotService } from './enhanced-screenshot'
+import { tradingViewAutomation } from './tradingview-automation'
+
+class ProcessCleanup {
+  private static instance: ProcessCleanup
+  private isShuttingDown = false
+
+  private constructor() {
+    // Register cleanup handlers
+    process.on('SIGINT', this.handleShutdown.bind(this))
+    process.on('SIGTERM', this.handleShutdown.bind(this))
+    process.on('SIGQUIT', this.handleShutdown.bind(this))
+    process.on('uncaughtException', this.handleError.bind(this))
+    process.on('unhandledRejection', this.handleError.bind(this))
+  }
+
+  static getInstance(): ProcessCleanup {
+    if (!ProcessCleanup.instance) {
+      ProcessCleanup.instance = new ProcessCleanup()
+    }
+    return ProcessCleanup.instance
+  }
+
+  private async handleShutdown(signal: string): Promise<void> {
+    if (this.isShuttingDown) {
+      console.log('Already shutting down, forcing exit...')
+      process.exit(1)
+    }
+
+    this.isShuttingDown = true
+    console.log(`\n🛑 Received ${signal}, initiating graceful shutdown...`)
+
+    try {
+      // Clean up screenshot service
+      console.log('🧹 Cleaning up screenshot service...')
+      await enhancedScreenshotService.cleanup()
+
+      // Clean up trading view automation
+      console.log('🧹 Cleaning up TradingView automation...')
+      await tradingViewAutomation.forceCleanup()
+
+      console.log('✅ Graceful shutdown completed')
+      process.exit(0)
+    } catch (error) {
+      console.error('❌ Error during shutdown:', error)
+      process.exit(1)
+    }
+  }
+
+  private async handleError(error: Error): Promise<void> {
+    console.error('❌ Unhandled error:', error)
+    
+    // Attempt cleanup
+    try {
+      await enhancedScreenshotService.cleanup()
+      await tradingViewAutomation.forceCleanup()
+    } catch (cleanupError) {
+      console.error('❌ Error during error cleanup:', cleanupError)
+    }
+    
+    process.exit(1)
+  }
+
+  // Manual cleanup method
+  async cleanup(): Promise<void> {
+    await this.handleShutdown('MANUAL')
+  }
+}
+
+// Initialize the cleanup handler
+const processCleanup = ProcessCleanup.getInstance()
+
+export default processCleanup