feat(settings): Notifications section skeleton + All-notifications toggle

Marks .notifications implemented, adds the shared setNotifications save
path (per-event subscribe/unsubscribe, sequential calls for toggles that
group more than one wire event type) and the master "All notifications"
row. Individual event toggles land in follow-up commits.

Outpost/Features/Account/SettingsView.swift

@@ -39,6 +39,8 @@ struct SettingsView: View {
     @State private var isShowingDeleteAccountConfirmation = false
     @State private var isDeletingAccount = false
     @State private var deleteAccountErrorMessage: String?
+    @State private var isSavingNotifications = false
+    @State private var notificationsErrorMessage: String?
 
     /// Full Local Sync and cache-clearing both need a real connection to be
     /// safe — clearing while offline (or letting Full Local Sync think it
@@ -79,6 +81,7 @@ struct SettingsView: View {
         case .appearance: appearanceDetail
         case .profile: profileDetail
         case .preferences: preferencesDetail
+        case .notifications: notificationsDetail
         case .offlineSync: offlineSyncDetail
         case .advanced: advancedDetail
         case .about: aboutDetail
@@ -544,6 +547,84 @@ struct SettingsView: View {
         }
     }
 
+    // MARK: - Notifications
+
+    private var notificationsDetail: some View {
+        VStack(alignment: .leading, spacing: 14) {
+            sectionHeader
+            Text("Manage when and where you receive email notifications.")
+                .font(.subheadline)
+                .foregroundStyle(.secondary)
+
+            if !isEffectivelyOnline {
+                offlineSettingsHint
+            }
+
+            allNotificationsRow
+            Divider()
+
+            if let notificationsErrorMessage {
+                Text(notificationsErrorMessage)
+                    .font(.caption)
+                    .foregroundStyle(.red)
+            }
+        }
+        .disabled(!isEffectivelyOnline)
+        .frame(maxWidth: 480, alignment: .leading)
+        .task { await refreshProfile() }
+    }
+
+    private var allNotificationsRow: some View {
+        let isOn = NotificationEventType.allCases.allSatisfy { session.userNotificationSettings?[$0.rawValue] ?? false }
+        return notificationToggleRow(
+            "All notifications",
+            description: nil,
+            isOn: isOn,
+            onChange: { newValue in Task { await setNotifications(nil, subscribed: newValue) } }
+        )
+    }
+
+    private func notificationToggleRow(
+        _ title: String,
+        description: String?,
+        isOn: Bool,
+        onChange: @escaping (Bool) -> Void
+    ) -> some View {
+        Toggle(isOn: Binding(get: { isOn }, set: onChange)) {
+            VStack(alignment: .leading, spacing: 2) {
+                Text(title)
+                if let description {
+                    Text(description)
+                        .font(.caption)
+                        .foregroundStyle(.secondary)
+                }
+            }
+        }
+    }
+
+    /// `eventTypes` groups more than one wire event under a single visible
+    /// toggle (e.g. "Mentioned" covers both `comments.mentioned` and
+    /// `documents.mentioned`) — confirmed as the right grouping against
+    /// Outline's own settings copy, applied with one subscribe/unsubscribe
+    /// call per underlying event type, sequentially.
+    private func setNotifications(_ eventTypes: [NotificationEventType]?, subscribed: Bool) async {
+        guard let apiClient = session.apiClient else { return }
+        isSavingNotifications = true
+        defer { isSavingNotifications = false }
+        let targets: [NotificationEventType?] = eventTypes ?? [nil]
+        do {
+            for target in targets {
+                let updated = subscribed
+                    ? try await apiClient.subscribeToNotifications(eventType: target)
+                    : try await apiClient.unsubscribeFromNotifications(eventType: target)
+                session.applyUpdatedProfile(updated)
+            }
+            notificationsErrorMessage = nil
+        } catch {
+            notificationsErrorMessage = outlineErrorMessage(error, fallback: "Couldn't update your notification settings.")
+        }
+    }
+
     // MARK: - Offline & Sync
 
     private var offlineSyncDetail: some View {

Outpost/Root/AppNavigation.swift

@@ -122,7 +122,7 @@ enum SettingsSection: String, CaseIterable, Identifiable, Hashable {
     /// placeholder until its content is specified and built.
     var isImplemented: Bool {
         switch self {
-        case .appearance, .offlineSync, .advanced, .about, .profile, .preferences:
+        case .appearance, .offlineSync, .advanced, .about, .profile, .preferences, .notifications:
             return true
         default:
             return false