Send daily review summaries with delay to wait for reviews from other devices to be synced

[RisingOrange]

Currently there is an issue with sending daily review summaries:

Example scenario: Day 1: User reviews cards on mobile, then syncs with AnkiWeb Day 2: User launches Anki Desktop, and automatically syncs with AnkiHub and AnkiWeb.

The issue is that on day 2, things happen in this order:

• AnkiHub sync, which among other things, sends the review data from Day 1 to the web app
• AnkiWeb sync, which adds the reviews done on mobile on Day 1 to Anki's database

So, the reviews done on mobile on day 1 will be missing from our data on the web app.

Related issues

Proposed changes

• Only send review data from x days ago.
  • For example, if a user syncs every day, we would send the summary for date.today() - timedelta(days=x) every day
  • We can assume that the further in the past the reviews were done, the higher the chance that they were already synced across all devices.
• Update tests
• Add test