fix(streaming): decompress upstream chunks for Google SSE

Google sends gzip-compressed SSE streams; aiter_raw() passed raw bytes
through, causing Janitor AI to see binary garbage and fail with
'Failed to fetch'. Switch to aiter_bytes() so httpx decompresses
on the fly before yielding chunks.

proxy/client.py

@@ -78,7 +78,7 @@ async def _stream_response(provider: Provider, real_key: str, body: dict[str, An
                 content = await upstream.aread()
                 detail = _upstream_error_message(upstream.status_code, content)
                 raise HTTPException(status_code=upstream.status_code, detail=detail)
-            async for chunk in upstream.aiter_raw():
+            async for chunk in upstream.aiter_bytes():
                 yield chunk