Keep workers alive on bad attachments and unreadable sources

[wuercher]

pdf2json can throw an unhandled rejection deep in image parsing (e.g. "Bits per component missing in image") that bypasses the pdfParser error events and crashes the indexing worker. As the workers run under concurrently, the crashed worker is not restarted and all indexing silently halts while emails keep being archived.

• Re-enable the safety timeout in extractTextFromPdf so a hung parse resolves empty instead of leaving the promise (and the indexing job) pending forever.
• Add unhandledRejection/uncaughtException guards to the indexing and ingestion workers so a single bad attachment, or an unreadable/locked source file (EACCES ReadStream error), cannot take the whole worker down.

Fixes #398

[github-actions]

Thank you for your submission, we really appreciate it. Like many open-source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution. You can sign the CLA by just posting a Pull Request Comment same as the below format.

---

I have read the CLA Document and I hereby sign the CLA

---

_{You can retrigger this bot by commenting recheck in this Pull Request. Posted by the CLA Assistant Lite bot.}