Move `manage.py` content to `evap.main` #3809

Job	Run time
MyPy	1m 29s
Linter	2m 9s
Test (shuffled order)	2m 20s
Test + Coverage	2m 47s
Backup process	3m 25s
Compile Scss	1m 37s
Formatting	1m 30s
Build nix environment on MacOS	3m 48s
Render Html pages	1m 53s
Test Typescript	1m 55s
	22m 53s

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