feat(contacts): calendar-wide reminders for special-dates calendars

Managed calendars now treat reminders as a calendar-level setting instead of the
seed-once-per-event model, matching how these homogeneous birthday/anniversary
calendars are actually used.

- New per-type "Reminders" control in the Contact special dates section. Changing
  it persists the per-calendar all-day override (so new events match) AND
  re-applies the set to *all existing events* in that calendar
  (CalendarDataSource.applyManagedCalendarReminders → SpecialDatesSyncEngine
  .applyReminders), encoding each event's all-day offset from its own date.
- Settings → Notifications: the contact-date calendars no longer offer a
  per-calendar override row; they show a link that jumps to the Contact special
  dates section (managedCalendarIds now in SettingsUiState).

Tests cover applyReminders (override persisted + bulk-apply invoked, and None
clears). lint + unit tests + assembleDebug green.

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

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

@@ -190,6 +190,18 @@ internal class FakeCalendarDataSource : CalendarDataSource {
         return id
     }
 
+    /** (calendarId, allDayTime, minutes) recorded from applyManagedCalendarReminders. */
+    val appliedManagedReminders = mutableListOf<Triple<Long, Int, List<Int>>>()
+
+    override fun applyManagedCalendarReminders(
+        calendarId: Long,
+        allDayReminderTimeMinutes: Int,
+        minutes: List<Int>,
+    ) {
+        writeError?.let { throw it }
+        appliedManagedReminders += Triple(calendarId, allDayReminderTimeMinutes, minutes)
+    }
+
     override fun updateManagedFields(eventId: Long, values: Map<String, Any?>) {
         writeError?.let { throw it }
         if (values.isEmpty()) return

app/src/test/java/de/jeanlucmakiola/calendula/data/contacts/SpecialDatesSyncEngineTest.kt

@@ -7,6 +7,7 @@ import androidx.datastore.preferences.core.Preferences
 import com.google.common.truth.Truth.assertThat
 import de.jeanlucmakiola.calendula.data.calendar.FakeCalendarDataSource
 import de.jeanlucmakiola.calendula.data.calendar.ManagedEventRow
+import de.jeanlucmakiola.calendula.data.prefs.CalendarReminderOverride
 import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
 import de.jeanlucmakiola.calendula.domain.contacts.ContactSpecialDate
 import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
@@ -163,6 +164,38 @@ class SpecialDatesSyncEngineTest {
         assertThat(settings.specialDatesCalendars.first()).doesNotContainKey(SpecialDateType.Anniversary)
     }
 
+    @Test
+    fun `applyReminders persists the override and applies it to all events`(@TempDir tempDir: Path) = runTest {
+        val calendars = FakeCalendarDataSource()
+        val contacts = FakeContacts(dates = listOf(birthday("a", "Jane", 5, 14, 1990)))
+        val (engine, settings) = engineWith(tempDir, contacts, calendars)
+        engine.sync(today)
+        val birthdayCal = settings.specialDatesCalendars.first().getValue(SpecialDateType.Birthday)
+
+        engine.applyReminders(SpecialDateType.Birthday, CalendarReminderOverride.Minutes(listOf(0, 1440)))
+
+        // Persisted as the per-calendar all-day override (so new events match)...
+        assertThat(settings.perCalendarAllDayReminderOverride.first()[birthdayCal])
+            .isEqualTo(listOf(0, 1440))
+        // ...and applied to the existing events in that calendar.
+        assertThat(calendars.appliedManagedReminders).contains(
+            Triple(birthdayCal, settings.allDayReminderTimeMinutes.first(), listOf(0, 1440)),
+        )
+    }
+
+    @Test
+    fun `applyReminders with None clears the reminders`(@TempDir tempDir: Path) = runTest {
+        val calendars = FakeCalendarDataSource()
+        val (engine, settings) = engineWith(tempDir, FakeContacts(), calendars)
+        engine.sync(today)
+        val birthdayCal = settings.specialDatesCalendars.first().getValue(SpecialDateType.Birthday)
+
+        engine.applyReminders(SpecialDateType.Birthday, CalendarReminderOverride.None)
+
+        assertThat(settings.perCalendarAllDayReminderOverride.first()[birthdayCal]).isEmpty()
+        assertThat(calendars.appliedManagedReminders.last().third).isEmpty()
+    }
+
     // --- pure diff ---
 
     private fun desired(uid: String, title: String, dt: Long, rrule: String? = "FREQ=YEARLY") =