Fix SSE connection handling and optimize Dockerfile

- Fixed SSE connection not being properly closed when pod logs dialog is closed
- Added proper cleanup for EventSource connections in K8sResourceList.tsx
- Added debugging logs to track SSE connection lifecycle
- Optimized Dockerfile to avoid copying frontend files during Go build stage
- Fixed backend handler to properly use context from request for log streaming

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docker-entrypoint.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+
+# Start the Go backend in the background
+/app/cluster -address 127.0.0.1:9119 -data-dir /data &
+
+# Wait a moment for backend to start
+sleep 2
+
+# Start nginx in the foreground
+nginx -g 'daemon off;'