Cron job to remove outdated uploaded chunks

[varmar05]

Added celery job to regularly remove outdated chunks.

[coveralls]

Pull Request Test Coverage Report for Build 16770575946

Details

• 46 of 50 (92.0%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.001%) to 91.974%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
server/mergin/sync/tasks.py	11	12	91.67%
server/mergin/sync/utils.py	9	12	75.0%

Files with Coverage Reduction	New Missed Lines	%
server/mergin/sync/utils.py	1	84.4%

Totals
Change from base Build 16745450194:	0.001%
Covered Lines:	7231
Relevant Lines:	7862

---

💛 - Coveralls