Make mainSetting a function that builds the section list itself

Convert the @mainactor let to func mainSetting(featureFlags:) so the
notifications section can be inserted at the right slot — between
advancedSettings and the trailing Celestia PLUS + misc sections —
without the caller calculating settings.count - 2. The Catalyst /
feature-flag gate now lives next to the insertion.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: levinli303

MobileCelestia/MainViewController.swift

@@ -1358,14 +1358,7 @@ Device Model: \(model)
 
     @objc private func showSettings() {
         let executor = self.executor
-        var settings = mainSetting
-        #if !targetEnvironment(macCatalyst)
-        if featureFlags.pushNotificationIOS {
-            // Insert just above the trailing Celestia PLUS + misc sections.
-            let insertIndex = max(0, settings.count - 2)
-            settings.insert(notificationsSettingSection, at: insertIndex)
-        }
-        #endif
+        let settings = mainSetting(featureFlags: featureFlags)
         let controller = SettingsCoordinatorController(
             core: core,
             executor: executor,

MobileCelestia/Settings/SettingsModel.swift

@@ -139,7 +139,7 @@ let notificationsSettingSection: SettingSection = SettingSection(
 )
 
 @MainActor
-let mainSetting: [SettingSection] = {
+func mainSetting(featureFlags: FeatureFlags) -> [SettingSection] {
     var items = [
         displaySettings(),
         timeAndRegionSettings(),
@@ -171,7 +171,12 @@ let mainSetting: [SettingSection] = {
         ]),
         advancedSettings(extraItems: advanceSettingExtraItems),
     ]
+    #if !targetEnvironment(macCatalyst)
+    if featureFlags.pushNotificationIOS {
+        items.append(notificationsSettingSection)
+    }
+    #endif
     items.append(celestiaPlusSettings())
     items.append(miscSettings())
     return items
-}()
+}