Create weekly Github Action to run integration tests

[nifadyev]

Now, the only way to get notified about Toggl API changes is to get error during pydantic schemas processing. That is why API requests via integration tests should be run periodically.

Pass env secretly, pre-delete projects or smth for smooth test execution
test_list_time_entries__no_result and test_bulk_edit_projects are now flaky

Use this snippet for repeated action:

on:
  schedule:
    - cron: '0 0 * * 1'