fix(contacts): keep distinct custom dates instead of collapsing them

The mirror keyed each event on (contact, type) only, and the read deduped on
that same pair from an unordered query. So a contact with two custom dates
('Wedding', 'Graduation') mirrored just one — and, the winner being
order-dependent, the single event could ping-pong between the two dates across
syncs. A Custom date's UID now carries a discriminator (its label, else its
month-day), the read dedups on the full UID, and the query is ordered by
Data._ID so a genuine duplicate resolves the same way every time.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/src/main/java/de/jeanlucmakiola/calendula/data/contacts/ContactSpecialDatesDataSource.kt

@@ -10,6 +10,7 @@ import androidx.core.content.ContextCompat
 import dagger.hilt.android.qualifiers.ApplicationContext
 import de.jeanlucmakiola.calendula.domain.contacts.ContactSpecialDate
 import de.jeanlucmakiola.calendula.domain.contacts.SpecialDateType
+import de.jeanlucmakiola.calendula.domain.contacts.managedUid
 import de.jeanlucmakiola.calendula.domain.contacts.parseContactEventDate
 import javax.inject.Inject
 import javax.inject.Singleton
@@ -50,9 +51,12 @@ class AndroidContactSpecialDatesDataSource @Inject constructor(
     override fun readSpecialDates(): List<ContactSpecialDate> {
         if (!hasPermission()) return emptyList()
         val resolver = context.contentResolver
-        // A contact can carry the same date more than once (multiple raw
-        // contacts under one aggregate); keep the first per (contact, type).
-        val seen = HashSet<Pair<String, SpecialDateType>>()
+        // A contact can carry the same date more than once (multiple raw contacts
+        // under one aggregate); dedup on the mirror's reconciliation key so exact
+        // duplicates collapse while genuinely distinct dates (two custom events on
+        // one contact) are all kept. Ordered by Data._ID so which of two truly
+        // conflicting rows wins is stable across syncs (no event ping-pong).
+        val seen = HashSet<String>()
         val result = ArrayList<ContactSpecialDate>()
         runCatching {
             resolver.query(
@@ -60,7 +64,7 @@ class AndroidContactSpecialDatesDataSource @Inject constructor(
                 PROJECTION,
                 "${ContactsContract.Data.MIMETYPE} = ?",
                 arrayOf(Event.CONTENT_ITEM_TYPE),
-                null,
+                "${ContactsContract.Data._ID} ASC",
             )?.use { c ->
                 val idxDate = c.getColumnIndexOrThrow(Event.START_DATE)
                 val idxType = c.getColumnIndexOrThrow(Event.TYPE)
@@ -71,8 +75,7 @@ class AndroidContactSpecialDatesDataSource @Inject constructor(
                     val lookup = c.getString(idxLookup)?.takeIf { it.isNotEmpty() } ?: continue
                     val parts = parseContactEventDate(c.getString(idxDate)) ?: continue
                     val type = specialDateTypeForRawEventType(c.getInt(idxType))
-                    if (!seen.add(lookup to type)) continue
-                    result += ContactSpecialDate(
+                    val date = ContactSpecialDate(
                         lookupKey = lookup,
                         displayName = c.getString(idxName)?.trim().orEmpty(),
                         type = type,
@@ -81,6 +84,7 @@ class AndroidContactSpecialDatesDataSource @Inject constructor(
                         year = parts.year,
                         label = c.getString(idxLabel)?.takeIf { it.isNotBlank() },
                     )
+                    if (seen.add(date.managedUid())) result += date
                 }
             }
         }.onFailure { Log.w(TAG, "Reading contact special-dates failed", it) }

app/src/main/java/de/jeanlucmakiola/calendula/domain/contacts/SpecialDateFormatting.kt

@@ -3,12 +3,40 @@ package de.jeanlucmakiola.calendula.domain.contacts
 import kotlinx.datetime.LocalDate
 
 /**
- * The deterministic `Events.UID_2445` that ties a mirrored event to its source
- * contact date. Stable across syncs (the reconciliation key), and namespaced by
- * type so the same contact's birthday and anniversary never collide.
+ * Prefix of every managed-event `UID_2445`. Distinguishes mirror events from
+ * user-created ones (which carry a random `<uuid>@calendula` UID), so the sync
+ * only ever reconciles — and never deletes — events it actually owns.
  */
-fun managedEventUid(type: SpecialDateType, lookupKey: String): String =
-    "contact-${type.name.lowercase()}:$lookupKey@calendula"
+const val MANAGED_UID_PREFIX = "contact-"
+
+/**
+ * The deterministic `Events.UID_2445` that ties a mirrored event to its source
+ * contact date. Stable across syncs (the reconciliation key), namespaced by
+ * type so the same contact's birthday and anniversary never collide, and — when
+ * a [discriminator] is given — by it too, so two Custom dates on one contact
+ * (e.g. "Wedding" and "Graduation") get distinct events instead of clobbering
+ * each other.
+ */
+fun managedEventUid(type: SpecialDateType, lookupKey: String, discriminator: String? = null): String {
+    val disc = discriminator?.takeIf { it.isNotBlank() }?.let { ":$it" }.orEmpty()
+    return "$MANAGED_UID_PREFIX${type.name.lowercase()}:$lookupKey$disc@calendula"
+}
+
+/**
+ * The reconciliation key for this date's mirrored event. Birthdays/anniversaries
+ * are one-per-contact, so they key on the contact alone; a [SpecialDateType.Custom]
+ * date adds a discriminator (its label, else its month-day) so distinct custom
+ * dates on one contact don't collapse into a single event.
+ */
+fun ContactSpecialDate.managedUid(): String =
+    managedEventUid(type, lookupKey, customDiscriminator())
+
+private fun ContactSpecialDate.customDiscriminator(): String? =
+    if (type == SpecialDateType.Custom) {
+        label?.trim()?.lowercase()?.ifBlank { null } ?: "%02d-%02d".format(month, day)
+    } else {
+        null
+    }
 
 /**
  * The all-day date the recurring `FREQ=YEARLY` series is anchored at: the real