Event: extract EventReader/EventWriter

[rfc2822]

Event is a data class and as such it shouldn't have hidden logic.

This PR extracts reading/writing Events into respective classes.

(In a later stage of refactoring, we will be able to completely remove the Event class and map directly between iCalendar ↔ Android data rows.)

To be merged for bitfireAT/davx5-ose#1573

[Copilot]

Pull Request Overview

This PR pulls the reading and writing logic out of the Event data class into new EventReader and EventWriter classes, updating all tests to use the new APIs and removing hidden behavior from Event.

• Introduces EventReader/EventWriter and migrates all Event.eventsFromReader/Event.write calls.
• Removes read/write methods and companion object from Event.
• Updates unit and instrumentation tests to use the new reader/writer and cleans up legacy code.

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
EventValidatorTest.kt	Replaced static reader calls with eventReader.readEvents; added eventReader property.
EventWriterTest.kt	New tests validating EventWriter.write output.
EventTest.kt (unit tests)	Added tests for Event.toString and organizerEmail accessor.
EventReaderTest.kt	Renamed test class, removed legacy code, switched to EventReader.readEvents.
EventWriter.kt	New class extracting write logic from Event.
EventReader.kt	New class extracting read logic from Event.
Event.kt	Stripped out read/write logic and companion object from Event.
Ical4jTest.kt (androidTest)	Updated to call EventReader.readEvents.

[sunkup]

Looks good 👍