feat(sharing): hidden-profile toggle + hide non-sharing group members

- UserProfile decodes directory_hidden; updateProfile() sends it; Settings has
  a "hide my profile" toggle (excludes you from share/group pickers).
- GroupMember decodes shares_calendar; the group filter list now only shows
  members who actually share a calendar (no phantom empty rows).
- Robust custom decoders (decodeIfPresent) for the new fields.

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

Calendarr iOS/Views/CalendarFilterSheet.swift

@@ -217,7 +217,9 @@ struct CalendarFilterSheet: View {
         if let g = groupDetail {
             List {
                 Section(header: Label(g.name, systemImage: GroupIcons.symbol(g.icon))) {
-                    ForEach(g.members ?? []) { m in
+                    // Only members who actually share a calendar into the group —
+                    // avoids phantom empty rows for members who share nothing.
+                    ForEach((g.members ?? []).filter { $0.sharesCalendar }) { m in
                         groupRow(name: m.displayName ?? "—",
                                  colorHex: m.color ?? "#4285f4",
                                  key: CalendarStore.groupMemberKey(m.id))

Calendarr iOS/Views/SettingsView.swift

@@ -32,6 +32,7 @@ struct SettingsView: View {
     @State private var privateVisibility = "busy"
     @State private var groupVisibleId = 0      // 0 = none
     @State private var ownLocalCals: [LocalCalendar] = []
+    @State private var directoryHidden = false
     @State private var profileMsg = ""
 
     var body: some View {
@@ -102,6 +103,13 @@ struct SettingsView: View {
                     .keyboardType(.emailAddress)
                     .autocapitalization(.none)
             }
+            Toggle(isOn: $directoryHidden) {
+                VStack(alignment: .leading, spacing: 2) {
+                    Text(L10n.t("settings.directory_hidden", appLang))
+                    Text(L10n.t("settings.directory_hidden.desc", appLang))
+                        .font(.caption).foregroundStyle(.secondary)
+                }
+            }
             Button(L10n.t("event.save", appLang)) { Task { await saveProfile() } }
             if !profileMsg.isEmpty {
                 Text(profileMsg).font(.caption).foregroundStyle(.secondary)
@@ -188,6 +196,7 @@ struct SettingsView: View {
             displayName = p.displayName ?? p.username
             loginName = p.username
             email = p.email ?? ""
+            directoryHidden = p.directoryHidden
         }
         if let s = try? await api.getSettings() {
             privateVisibility = s.privateEventVisibility
@@ -202,7 +211,8 @@ struct SettingsView: View {
         do {
             _ = try await api.updateProfile(displayName: displayName.isEmpty ? nil : displayName,
                                             username: nil,
-                                            email: email.isEmpty ? "" : email)
+                                            email: email.isEmpty ? "" : email,
+                                            directoryHidden: directoryHidden)
             UserDefaults.standard.set(displayName, forKey: "displayName")
             profileMsg = L10n.t("settings.saved", appLang)
         } catch {