Release 0.81.0

What's Changed

Fixes

• Fix series rescheduling for today if has ongoing or past reservation by @matti-lamppu in #1451
• Remove celery ping health check due to unreliability by @matti-lamppu in #1454

Updates

• Update Ruff and configuration by @ranta in #1449
• Remove deprecated features by @matti-lamppu in #1452

Automated

• [pre-commit.ci] pre-commit autoupdate by @pre-commit-ci in #1450

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Full Changelog: v0.80.0...v0.81.0