Morango upgrade and sync queue tweaks

[rtibbles]

Summary

• Updates morango to version that has syncing_objects as the manager used for Morango syncing
• Adds syncing_objects to Collection proxy classes to ensure proper filtering of synced collections
• Updates the public SyncQueue endpoint allows soft deleted, deleted, and hard deleted users to still queue for a sync, to ensure that their deletion can be propagated to an LoD.
• Adds tests to cover soft deleted users being able to use the sync queue, and deleted, and hard deleted users that have and have not been serialized to the store.

References

This was noticed by @AlexVelezLl while implementing #13759

Reviewer guidance

All production code implementation was done by hand - initial tests were written by Claude Code and then tweaked.

Have I covered every possibility for the sync cases? Will allowing the SyncQueue actually allow the sync to happen, or do we need more tweaks for that?

Hrm, to answer my own question, I think we might need more.

[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.19.0b0.dev0_git.44.gbcff3cf2.pex
Windows Installer (EXE)	kolibri-0.19.0b0.dev0+git.44.gbcff3cf2-windows-setup-unsigned.exe
Debian Package	kolibri_0.19.0b0.dev0+git.44.gbcff3cf2-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.19.0b0.dev0+git.44.gbcff3cf2.dmg
Android Package (APK)	kolibri-0.19.0b0.dev0+git.44.gbcff3cf2-0.1.6-debug.apk
Raspberry Pi Image	kolibri-pi-image-0.19.0b0.dev0+git.44.gbcff3cf2.zip
TAR file	kolibri-0.19.0b0.dev0+git.44.gbcff3cf2.tar.gz
WHL file	kolibri-0.19.0b0.dev0+git.44.gbcff3cf2-py2.py3-none-any.whl

[rtibbles]

Hrm, postgres still complaining about transaction isolation in the test. Will try to find a better way to handle this.

[bjester]

Changes make sense to me