[LeonardNJU]

Summary

• Serialize files selected from the Nextcloud Files page instead of starting all transfers concurrently through the Bulwark plugin proxy.
• Queued uploads can be cancelled and later resumed without duplicate starts.
• Add regression tests for sequential multi-file upload and queued cancel/resume.

Motivation

On a self-hosted Bulwark 1.17.0 and Nextcloud 33 deployment running Nextcloud plugin 1.1.1, choosing three small files caused only one to reach Nextcloud (WebDAV PUT 201). The other two displayed a connection error and did not reach the Bulwark proxy.
The affected user confirmed that uploads work after deploying a sequential-queue patch. This avoids bursts of browser-to-proxy uploads, although the precise transport failure is not yet established.

Verification

• npm test -- --run nextcloud: 129 passing tests
• npm run check: 25 plugins checked successfully
• git diff --check: clean

Only source and tests are changed. No credentials or generated artifacts included.