fix: make streaming uploads opt-in for backwards compatibility

Streaming multipart uploads (introduced in 0.24.0) caused 400 errors
with some servers that don't handle chunked transfer encoding well.

This changes streaming from opt-out (stream_body: false) to opt-in
(stream_body: true) to preserve backwards compatibility.

Users who want memory-efficient large file uploads can explicitly
enable streaming with stream_body: true.

Fixes #832

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Release 0.24.1

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Release 0.24.0

Release 0.23.2

Release 0.23.1

Release 0.23 with foul mode

master => main

Update version

Release 0.20

Release 0.19.1