Automatically update today view on date change

[MarSoft]

This fixes #633 Things to improve: when the user changes day start in config, we should probably perform update_today too. Not sure though; anyway, this situation is not so frequent.

[github-actions[bot]]

Automatically generated build artifacts for commit ace8013b1cbf11f1761caa8bb16c5fe9ab601ca8 (note: these links will expire after some time):

• Flatpak application: :arrow_double_down: Download

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To test this PR, download and unzip the flatpak application above and then install with:

flatpak install Hamster.flatpak

[MarSoft]

Using the version with this PR applied every day for more than 3 months, works fine.