* fix(wecom): raise the image upload cap to the platform's 10 MB
`send_file` capped images at 2 MB and files at 20 MB. 2 MB is the *voice*
limit in WeCom's aibot media-upload protocol; images are allowed up to 10 MB
(developer.work.weixin.qq.com/document/path/101917). Every 2-10 MB image was
therefore dropped before upload, and the turn arrived without its chart.
Raise the image cap to 10 MB. The 512 KiB chunk size keeps a 10 MB upload at
20 chunks, well under the protocol's 100-chunk limit.
* docs(changelog): record the WeCom image-cap fix
Adds the Unreleased -> Fixed -> channels entry for #8174 to CHANGELOG.md and
CHANGELOG_zh.md.
51cc489c8f