- Use ffmpeg CLI directly for HEIC/HEIF previews (bypassing pyvips which
cannot encode >8-bit AVIF on current system). ffmpeg handles tile
assembly, EXIF rotation, HDR metadata and ICC profiles automatically.
- pyvips remains primary for other image formats; ffmpeg is fallback.
- Simplify _get_image_dimensions() to use pyvips header read for all
formats including HEIC, with ffprobe as fallback.
- Move all imports to top of preview.py; remove lazy OnlyOffice import.
- Worker pool: add readiness handshake (\x01 byte), bounded idle wait
with PREVIEW_TIMEOUT, eager module import before signalling.
- Fix dispatch data check bug (was 'if data is not None' -> 'if data').
- Add logger.exception for unhandled preview/dispatch errors.
- EmojiFormatter now includes tracebacks for exception logs.
- Return 503 on preview timeouts instead of 504.
LeoVasanko
13f32c57ab