✨ Add predefined event-type system to create-event form

[lavigarg-simform]

Description

This PR adds a predefined event-type system to the example app, Google-Calendar
style: picking a type (Birthday, Task, Out of office, Meeting, Reminder, or the
default Event) preconfigures the create-event form. Example-only — the
calendar_view package API is untouched.

What's added

• EventType enum + event_types.dart — defines the types and their presets
  (kEventTypeConfigs: color, whole-day vs. timed, duration, recurrence, optional
  image). EventMetadata stores the chosen type on CalendarEventData.event so it
  travels with the event without changing the package API.

• Type picker in the form (add_event_form.dart) — a dropdown seeds color, time,
  duration, and recurrence from the selected type's preset. All values stay editable,
  and edited events remember their type. (The description field is no longer required.)

• Image-backed schedule tiles — when a type has a background image, the tile shows
  it as a hero background with a scrim and light text; other tiles keep the solid tint.
  A description preview line was also added.

• Details page — shows the localized event-type label when present.

• Demo data, assets & l10n — seeded events tagged with types, 5 background images,
  and new localization keys in app_en.arb, app_es.arb, and app_ar.arb.

Behavior change

The event description field is no longer required in the create-event form — its
mandatory validator was removed.

Checklist

• The title of my PR starts with a [Conventional Commit] prefix (fix:, feat:, docs: etc).
• I have followed the [Contributor Guide] when preparing my PR.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples or docs.

Breaking Change?

• Yes, this PR is a breaking change.
• No, this PR is not a breaking change.

Related Issues

None

Demo

predefined.events.demo.mp4

[Copilot]

Pull request overview

Adds a predefined event-type system to the example app (not the calendar_view package API), allowing users to choose a type (Birthday/Task/OOO/Meeting/Reminder/Event) that seeds the create-event form and enables image-backed schedule tiles, plus localized labels/descriptions.

Changes:

• Introduces EventType, EventTypeConfig presets, and EventMetadata stored in CalendarEventData.event (example-only payload).
• Updates the add/edit event form with an event-type dropdown that applies presets and makes description optional.
• Enhances schedule tiles and details page to display event-type visuals/labels; adds l10n keys for new strings.

Reviewed changes

Copilot reviewed 10 out of 15 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
example/lib/widgets/schedule_view/schedule_view_event_tile.dart	Adds image-backed tile rendering + description preview based on selected event type.
example/lib/widgets/add_event_form.dart	Adds type picker and preset application; removes description validator; stores EventMetadata.
example/lib/pages/home_page.dart	Seeds some demo events with EventMetadata(EventType...) and tightens the events list typing.
example/lib/pages/event_details_page.dart	Displays the localized event type label when present.
example/lib/l10n/app_en.arb	Adds English strings for event types and preset descriptions.
example/lib/l10n/app_es.arb	Adds Spanish strings for event types and preset descriptions.
example/lib/l10n/app_ar.arb	Adds Arabic strings for event types and preset descriptions.
example/lib/extension.dart	Adds extensions to read event type from payload + localize type label/description.
example/lib/event_types.dart	New file defining event-type presets and the EventMetadata payload.
example/lib/enumerations.dart	Adds EventType enum to the example’s enumerations.

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