qr_decoder: report results through module_status (part of #493)

[Nandika-Gupta]

Summary

Part of #493 (qr_decoder only). qr_decoder now reports its results through annotate instead of setting result["error"] directly, and "No QR code detected" is treated as an OK result, since the image was read fine.

Changes

• "No QR code detected in the image" is now OK with that reason in status_reason. This also covers the case where the online API finds no code, which used to come back as an error.
• API and network failures are ERROR, and a successful decode is OK.
• Frontend: the QR panel only rendered something when error was set, so "no QR code" would have shown empty rows. It now shows the status reason instead (2 lines in ToolPanels.tsx, and QrResult extends ModuleStatusFields).
• Added tests/test_qr_decoder.py with a test for each case: local decode, no QR code, API HTTP error, network error and API decode.

Type of change

• Bug fix
• New feature
• Breaking change
• Documentation update

Testing

• I have tested these changes locally
• I have added/updated tests as needed

git grep -n 'result\["error"\] =' modules/qr_decoder.py now returns nothing. pytest tests/test_qr_decoder.py passes (5 tests).

Screenshots

N/A

[github-actions]

Thanks for the first pull request here. CI needs a maintainer to approve the run before it starts, so it may sit for a bit before anything happens. pytest tests/ -q passing is the main thing I look at.

[NovaCode37]

Matches #493: no code in the image is an answer, an API failure is an error, and the panel now says so instead of showing nothing. Thanks.