* webui: export conversations as jsonl
each session is one jsonl file, a session header line followed by one line per message
exporting multiple conversations bundles them into a zip, one jsonl file each
* webui: import jsonl and zip conversation exports
parse the new jsonl session format and zip archives on import
keep supporting the legacy json format
* Add boilerplate for file types
* Add heic-to and implement conversion
* Load heic library from CDN
* Use jpg instead of png for conversion
* Move const to constants file
Julien Chaumond