feat: render server display_title for group events (consistent across clients)

CalEvent parses display_title; decorateGroup uses it (group icon + owner prefix
from the server) instead of the hardcoded glyph, with a fallback for older
servers. Raw title kept for editing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/java/com/scarriffle/calendarr/domain/model/CalEvent.kt

@@ -31,6 +31,9 @@ data class CalEvent(
     val owner: EventPerson? = null,
     val isGroupEvent: Boolean = false,
     val displayColor: String? = null,
+    // Server-decorated title for the group combined view (group icon / owner
+    // prefix); rendered in group mode while `title` stays raw for editing.
+    val displayTitle: String? = null,
 ) {
     /**
      * Group view supplies a server-resolved colour (display_color); otherwise
@@ -117,6 +120,7 @@ data class CalEvent(
                 owner = personFrom(json, "owner"),
                 isGroupEvent = json.optBoolean("is_group_event", false),
                 displayColor = json.strOrNull("display_color"),
+                displayTitle = json.strOrNull("display_title"),
             )
         }
     }

app/src/main/java/com/scarriffle/calendarr/ui/calendar/CalendarViewModel.kt

@@ -215,6 +215,10 @@ class CalendarViewModel @Inject constructor(
     private fun decorateGroup(events: List<CalEvent>): List<CalEvent> {
         val me = currentUserId
         return events.map { ev ->
+            // Prefer the server-decorated title (group icon + owner prefix) so
+            // web, iOS and Android render identically; fall back for old servers.
+            val serverTitle = ev.displayTitle?.takeIf { it.isNotEmpty() }
+            if (serverTitle != null) return@map ev.copy(title = serverTitle)
             val prefix = when {
                 ev.isGroupEvent && ev.creator != null && ev.creator.id != me -> "👥 ${firstName(ev.creator.displayName)}: "
                 ev.isGroupEvent -> "👥 "