[csutcliff]

Problem

When an upload is rejected with 406 (an invalid MD5 file, an unsupported file type), UploadFileService::handleError() calls request->send() and then closes the connection straight away so the client fails fast. ESPAsyncWebServer's send() only stores the response. It is written once the whole request body has been parsed, so the close always wins and the client gets no response at all. curl reports "Empty reply from server" (exit 52) instead of the 406.

Fix

Don't send or close in handleError() for 406. uploadComplete() already sends the stored error code once the body has arrived, as it does for every other code. The later chunks are already ignored once an error is recorded.

The cost is that a rejected large file is uploaded in full before the 406 arrives, the same as a firmware for the wrong chip (503) already behaves. The WebUI only offers .json, .bin and .md5, and shows the same message for any failed upload.

Testing

BBQKees Gateway E32 V2 (s_16M_P, with #3305 applied so the rejected uploads don't crash), curl to /rest/uploadFile:

Upload	Before	After
empty EMS-ESP.md5	Empty reply from server	406 in 0.17 s
EMS-ESP.md5 containing hello	Empty reply from server	406
notes.txt	Empty reply from server	406
1 MB big.zip		406 after the upload, 5.3 s
valid .md5 then .bin	ok	ok

• Builds for s_16M_P, clang-format clean.

The Recovery firmware's uploadFail() (recovery/main.cpp) closes the connection the same way after a 406. Not changed here.

Checklist

• Against the dev branch
• Formatted per .clang-format
• New logic is commented
• One fix only, only relevant files touched
• CHANGELOG_LATEST.md updated
• I accept the CLA in CONTRIBUTING.md