Add birthday feature (iOS)

- LocalCalendar/CalEvent gain is_birthday + birthday fields; API sends
  rrule/external_uid/birth_year and can create/update birthday calendars
- BirthdaysImporter: mirrors Contacts birthdays into a chosen birthday
  calendar, reconciling by external_uid (leaves manual entries untouched)
- AccountsView: "birthday calendar" toggle + notify-days when creating a
  calendar, and a "Birthdays from Contacts" section (enable + target + sync now)
- FAB long-press menu -> "New birthday" opens a minimal name+date mask
  (BirthdayEditorSheet) targeting birthday calendars, with year-unknown option
- Event bars render display_title (age) and a cake icon via EventLabel
- NSContactsUsageDescription added to both app build configs

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

Calendarr iOS/Models/CalEvent.swift

@@ -67,10 +67,17 @@ struct CalEvent: Identifiable, Hashable {
     var reminders: [Int] = []
     // True for events from a calendar shared with the user read-only.
     var readOnly: Bool = false
+    // True for events from a birthday calendar — clients show a cake icon and the
+    // server bakes the age into `displayTitle`.
+    var isBirthday: Bool = false
 
     // Group view supplies a server-resolved colour; otherwise per-event then calendar colour.
     var effectiveColor: String { displayColor ?? color ?? calendarColor }
 
+    // Title to render: the server-decorated one (birthday age, group prefix) wins
+    // over the raw title, which is kept for editing.
+    var renderTitle: String { displayTitle ?? title }
+
     static func from(json: [String: Any]) -> CalEvent? {
         guard
             let title = json["title"] as? String,
@@ -110,7 +117,8 @@ struct CalEvent: Identifiable, Hashable {
             displayColor: (json["display_color"] as? String).flatMap { $0.isEmpty ? nil : $0 },
             displayTitle: (json["display_title"] as? String).flatMap { $0.isEmpty ? nil : $0 },
             reminders: (json["reminders"] as? [Int]) ?? (json["reminders"] as? [Any])?.compactMap { ($0 as? Int) ?? Int("\($0)") } ?? [],
-            readOnly: json["read_only"] as? Bool ?? false
+            readOnly: json["read_only"] as? Bool ?? false,
+            isBirthday: json["is_birthday"] as? Bool ?? false
         )
     }
 }
@@ -174,3 +182,21 @@ func formatISO(_ date: Date, allDay: Bool) -> String {
     }
     return isoBasic.string(from: date)
 }
+
+/// Inline label for an event in a calendar grid: a leading birthday (cake) icon
+/// when the event is a birthday, followed by the render title (which carries the
+/// server-computed age). Icon and text inherit the surrounding font/colour, so
+/// the label matches whatever bar it's dropped into.
+struct EventLabel: View {
+    let event: CalEvent
+    var body: some View {
+        if event.isBirthday {
+            HStack(spacing: 3) {
+                Image(systemName: "birthday.cake.fill").imageScale(.small)
+                Text(event.renderTitle)
+            }
+        } else {
+            Text(event.renderTitle)
+        }
+    }
+}