fix(settings): label our own settings group "Outpost"

The general category (Appearance, Offline & Sync, Advanced, About)
sat unlabeled at the top of the sidebar, ambiguous next to the named
Outline categories below it. Now has its own "Outpost" header.

Outpost/Features/Account/SettingsSidebarList.swift

@@ -7,9 +7,10 @@ import SwiftUI
 /// clears `AppNavigation.isShowingSettings`, which puts the collections tree
 /// back.
 ///
-/// Grouped by `SettingsCategory` — `general` (ours) sits unlabeled at the
-/// top, then Outline's own Account/Workspace/Integrations & Installation
-/// groups, matching the settings page structure of the Outline web app.
+/// Grouped by `SettingsCategory` — `general` (ours) sits under an "Outpost"
+/// header at the top, then Outline's own Account/Workspace/Integrations &
+/// Installation groups, matching the settings page structure of the
+/// Outline web app.
 struct SettingsSidebarList: View {
     @Binding var selection: SettingsSection?
     let onDone: () -> Void

Outpost/Root/AppNavigation.swift

@@ -2,7 +2,8 @@ import Observation
 
 /// Top-level groupings shown as section headers in `SettingsSidebarList`.
 /// `general` holds everything that's ours, not Outline's own settings
-/// categories — no header, sits above the named groups.
+/// categories — labeled "Outpost" so it reads as clearly distinct from the
+/// Outline-sourced groups below it.
 enum SettingsCategory: String, CaseIterable, Identifiable {
     case general
     case account
@@ -13,7 +14,7 @@ enum SettingsCategory: String, CaseIterable, Identifiable {
 
     var title: String? {
         switch self {
-        case .general: return nil
+        case .general: return "Outpost"
         case .account: return "Account"
         case .workspace: return "Workspace"
         case .integrationsInstallation: return "Integrations & Installation"