[kg290]

Description

Let scheduled backups re-arm only after their result is handled. Refresh timers when a repository is changed or unset, and refresh offline schedule displays without losing paused status.

Related Issue

Fixes #2603.

Motivation and Context

Prevents immediate retries after a failed scheduled backup, missing-repository crashes, and stale schedule displays.

How Has This Been Tested?

Linux under WSL, Python 3.12 and Qt 6.12:

• uv run --no-sync pytest tests/unit/test_scheduler.py tests/unit/test_repo.py tests/unit/test_schedule.py tests/unit/test_jobs_table_model.py -q --tb=short — 196 passed with QT_QPA_PLATFORM=offscreen under dbus-run-session.
• Pre-commit checks passed for all changed files.
• Regression tests cover failed-run retries, manual re-arming, repository removal/reselection, and offline paused status.

The full multi-version test suite was not run.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist

• I have read the contributing guide.
• My code follows the project style.
• I have added tests to cover my changes.
• All new and existing tests passed (targeted tests only; see above).

No documentation changes are needed.

I provide this contribution under the repository license and affirm the Developer Certificate of Origin.

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