Apply upstream widget fixes (PR #289) to fork

[Copilot]

Ports EmmaTellblom#289 ("Widget fixes") into this fork. Widgets were not updating after calculation changes or across midnight/reboots.

New

• PeriodCalculationWidgetUpdater — singleton that diffs the last known next-period date and fires widget updates only on change; @Volatile for thread safety

Modified

• CalculationsHelper.nextPeriod() — calls PeriodCalculationWidgetUpdater.updateWidgetsIfPeriodChanged() on each DB-triggered recalculation
• DatabaseUtils.createDatabase() — adds missing databaseVersion11() call so fresh installs get the unique index on periods.date / ovulations.date
• app/build.gradle.kts — version bump 2.0 (24) → 2.1 (25)
• Widget string names — renamed to encode all four variants explicitly (with_label_with_bg, no_label_with_bg, with_label_no_bg, no_label_no_bg); widget provider XMLs updated accordingly
• gradlew — restored executable bit

Already present in this fork from PR #1: BootReceiver, BaseWidgetReceiver.onUpdate midnight-worker scheduling, MainActivity.updateWidgetsOnAppStart, and the corresponding AndroidManifest entries.

Original prompt

I have a fork from Mensinator source

In the repo there is a new pr 289 I want to make changes in my fork with that code

So I guess update my fork somehow?

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