feat(search): full-text event search from the top bar

A magnifier in each calendar screen's top bar opens a search overlay: type a
query and matching events (title, location or description) appear, nearest-to-
today first; tapping a result opens its detail.

- Data: query the Events table directly with a LIKE selection on title /
  description / location (wildcards escaped), so search is unbounded in time and
  filtered provider-side. New SearchProjection + toSearchResult mapper reuse the
  .ics export's DURATION handling for recurring masters. Hidden calendars are
  filtered out, mirroring instances().
- SearchViewModel debounces the query (250 ms), needs >= 2 chars, and orders
  results upcoming-ascending then past-descending.
- SearchScreen: autofocused inline field in the top bar, GroupedRow results
  reusing the agenda row style, idle/empty states. Hosted as a CalendarHost
  overlay below detail/edit so a tapped result's detail draws on top.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/test/java/de/jeanlucmakiola/calendula/data/calendar/FakeCalendarDataSource.kt

@@ -16,6 +16,7 @@ internal class FakeCalendarDataSource : CalendarDataSource {
 
     var calendarsResult: List<CalendarSource> = emptyList()
     var instancesResult: (Long, Long) -> List<EventInstance> = { _, _ -> emptyList() }
+    var searchResult: (String) -> List<EventInstance> = { _ -> emptyList() }
     var eventDetailResult: (Long) -> EventDetail? = { null }
     var eventColorPaletteResult: (Long) -> List<EventColorOption> = { emptyList() }
     var exportableEventsResult: List<IcsEvent> = emptyList()
@@ -51,6 +52,7 @@ internal class FakeCalendarDataSource : CalendarDataSource {
     override fun calendars(): List<CalendarSource> = calendarsResult
     override fun instances(beginMillis: Long, endMillis: Long): List<EventInstance> =
         instancesResult(beginMillis, endMillis)
+    override fun searchEvents(query: String): List<EventInstance> = searchResult(query)
     override fun eventDetail(eventId: Long): EventDetail? = eventDetailResult(eventId)
     override fun eventColorPalette(calendarId: Long): List<EventColorOption> =
         eventColorPaletteResult(calendarId)