[calendar] refactor: delegate event expansion to node-ical's expandRecurringEvent

[KristjanESPERANTO]

node-ical 0.25.x added expandRecurringEvent() — a proper API for expanding both recurring and non-recurring events, including EXDATE filtering and RECURRENCE-ID overrides. This PR replaces our hand-rolled equivalent with it.

calendarfetcherutils.js loses ~125 lines of code. What's left only deals with MagicMirror-specific concerns: timezone conversion, config-based filtering, and output formatting. The extra lines in the diff come from new tests.

What was removed

• getMomentsFromRecurringEvent() — manual rrule.js wrapping with custom date extraction
• isFullDayEvent() — heuristic with multiple fallback checks
• isFacebookBirthday workaround — patched years < 1900 and special-cased @facebook.com UIDs
• The if (event.rrule) / else split — all events now go through a single code path

Bugs fixed along the way

Both were subtle enough to go unnoticed before:

• [object Object] in event titles/description/location — node-ical represents ICS properties with parameters (e.g. DESCRIPTION;LANGUAGE=de:Text) as {val, params} objects. The old code passed them straight through. Mainly affected multilingual Exchange/O365 setups. Fixed with unwrapParameterValue().

• excludedEvents with until never worked — shouldEventBeExcluded() returned { excluded, until } but the caller destructured it as { excluded, eventFilterUntil }, so the until date was always undefined and events were never hidden. Fixed by correcting the destructuring key.

The expansion loop also gets error isolation: a single broken event is logged and skipped instead of aborting the whole feed.

Other clean-ups

• Replaced this.shouldEventBeExcluded with CalendarFetcherUtils.shouldEventBeExcluded — avoids context-loss bugs when the method is destructured or called indirectly.
• Replaced deprecated substr() with slice().
• Replaced now < filterUntil (operator overloading) with now.isBefore(filterUntil) — idiomatic Moment.js comparison.
• Fixed @returns JSDoc: string[] → object[].
• Moved verbose Log.debug("Processing entry...") after the VEVENT type guard to reduce log noise from non-event entries.
• Replaced JSON.stringify(event) debug log with a lightweight summary to avoid unnecessary serialization cost.
• Added comment explaining the 0-duration → end-of-day fallback for events without DTEND.

Tests

24 unit tests, all passing (npx vitest run tests/unit/modules/default/calendar/).

New coverage: excludedEvents with/without until, Facebook birthday year expansion, output object shape, no-DTEND fallback, error isolation, unwrapParameterValue, getTitleFromEvent, ParameterValue properties, RECURRENCE-ID overrides, DURATION (single and recurring).