feat(ui): simplify event date selection

[j-ordep]

Summary

• keep CreateEventScreen on single-date selection by default and gate multi-date selection behind an explicit checkbox
• extract reusable calendar selection helpers with unit coverage
• shorten participation CTAs to Confirmar / Confirmado to avoid uneven button wrapping

Testing

• npx tsc --noEmit
• npx tsc -p tsconfig.test.json --outDir C:/dev/mjcp/mobile/.tests-dist-event-calendar-ux
• compiled unit suite from C:/dev/mjcp/mobile/.tests-dist-event-calendar-ux/tests/*

[Copilot]

Pull request overview

This PR simplifies event date selection in CreateEventScreen by defaulting to a single-date selection and gating multi-date selection behind an explicit checkbox. It also extracts the selection logic into a reusable helper with unit tests, and shortens the participation CTA labels to Confirmar / Confirmado to avoid uneven button wrapping.

Changes:

• Extract toggleCalendarDateSelection and collapseCalendarSelectionToSingleDate helpers with unit tests, and use them in CreateEventScreen to drive a checkbox-gated multi-date mode.
• Shorten participation CTA labels in ScheduleScreen and EditScheduleScreen to Confirmar / Confirmado.
• Wire the new test file into mobile/package.json and document the UX decisions in mobile/docs/TASKS.md.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
mobile/src/utils/eventCalendarSelection.ts	New helper module for single/multi-date toggle and collapse logic.
mobile/tests/eventCalendarSelection.test.ts	Unit tests covering the new selection helpers.
mobile/src/screens/app/CreateEventScreen.tsx	Adds allowMultipleDates state, checkbox UI, and delegates day-press logic to the helper.
mobile/src/screens/app/ScheduleScreen.tsx	Shortens confirm CTA to Confirmar / Confirmado.
mobile/src/screens/app/EditScheduleScreen.tsx	Shortens confirm CTA to Confirmar / Confirmado.
mobile/package.json	Registers the new test file in the test:unit script.
mobile/docs/TASKS.md	Documents the CTA and single-date-by-default UX decisions.

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