Ignore recurrence rules whose UNTIL is on or before DTSTART

[rfc2822]

• calendar provider → VEVENT: filter invalid RRULE with UNTIL before DTSTART
• VEVENT → calendar provider: add test to show that such invalid RRULEs are no problem; so we don't need to manipulate them

[Copilot]

Pull Request Overview

This PR improves handling of invalid recurrence rules by filtering out RRULE and EXRULE instances where the UNTIL date is on or before the event's DTSTART date. The implementation moves validation from EventValidator to RecurrenceFieldsProcessor to prevent invalid rules from being created in the first place.

Key changes:

• Added filtering logic in RecurrenceFieldsProcessor to skip RRULE/EXRULE with invalid UNTIL dates
• Removed the validation and removal logic from EventValidator that previously handled these cases
• Added comprehensive tests to verify the new behavior works correctly

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
RecurrenceFieldsProcessor.kt	Added validation to filter out RRULE/EXRULE with UNTIL <= DTSTART during processing
EventValidator.kt	Removed validation methods and repair logic for invalid RRULE UNTIL dates
RecurrenceFieldProcessorTest.kt	Added tests for RRULE and EXRULE filtering, fixed class name typo
EventValidatorTest.kt	Removed all tests related to UNTIL validation that are no longer needed
AndroidCalendarProviderBehaviorTest.kt	Added test to verify invalid RRULE can still be inserted into calendar provider

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[sunkup]

Looks good, but see the comment.