StreamingResponse + forwarded content-length header was causing a
content-length mismatch (chunked vs explicit length), which made axios
reject the response even though doc-service had already saved the file.
Switch to Response, strip content-length/content-type from forwarded
response headers (FastAPI recalculates them correctly), and strip
accept-encoding from forwarded requests to prevent decompression
mismatches.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
