Add PYTHONUNBUFFERED=1 so startup logs flush promptly

Dockerfile

@@ -26,6 +26,10 @@ COPY data/ ./data/
 
 ENV GRADIO_SERVER_NAME=0.0.0.0
 ENV GRADIO_SERVER_PORT=7860
+# Without this, stdout is block-buffered in a non-TTY container: print()
+# output (our own startup/progress logs) sits unflushed while stderr-based
+# output (tqdm progress bars) appears immediately, making logs look stuck.
+ENV PYTHONUNBUFFERED=1
 EXPOSE 7860
 
 # rag_index/ is NOT copied at build time — it's 2.3GB (over the free-tier 1GB