Add feature flag to disable Trending functionality

Introduces a feature flag to disable the Trending section across the app. When disabled, all trending-related UI elements, navigation links, and settings are hidden.

Changes:
- Add trendingEnabled feature flag to FeatureFlags.swift (currently disabled)
- Hide Trending tab in AppTabNavigation, Sidebar, and TVNavigationView
- Remove Trending option from visible sections settings
- Remove Trending option from startup section picker
- Disable Trending menu command and keyboard shortcut
- Prevent Trending URL navigation in OpenURLHandler
- Hide Trending in FavoriteItemView navigation

Shared/FeatureFlags.swift

@@ -5,4 +5,8 @@ enum FeatureFlags {
     /// Controls whether the "Hide Shorts" functionality is available
     /// Set to false when the API changes prevent reliable detection of short videos
     static let hideShortsEnabled = false
+
+    /// Controls whether the "Trending" section is available
+    /// Set to false to disable trending functionality across the app
+    static let trendingEnabled = false
 }

Shared/Home/FavoriteItemView.swift

@@ -353,7 +353,7 @@ struct FavoriteItemView: View {
         case .history:
             return false
         case .trending:
-            return visibleSections.contains(.trending)
+            return FeatureFlags.trendingEnabled && visibleSections.contains(.trending)
         case .subscriptions:
             return visibleSections.contains(.subscriptions) && accounts.signedIn
         case .popular:

Shared/MenuCommands.swift

@@ -39,6 +39,7 @@ struct MenuCommands: Commands {
             Button("Trending") {
                 setTabSelection(.trending)
             }
+            .disabled(!FeatureFlags.trendingEnabled)
             .keyboardShortcut("4")
 
             Button("Search") {

Shared/Navigation/AppTabNavigation.swift

@@ -37,7 +37,7 @@ struct AppTabNavigation: View {
                         popularNavigationView
                     }
 
-                    if visibleSections.contains(.trending) {
+                    if FeatureFlags.trendingEnabled && visibleSections.contains(.trending) {
                         trendingNavigationView
                     }
 

Shared/Navigation/Sidebar.swift

@@ -101,7 +101,7 @@ struct Sidebar: View {
                     .id("popular")
                 }
 
-                if visibleSections.contains(.trending) {
+                if FeatureFlags.trendingEnabled && visibleSections.contains(.trending) {
                     NavigationLink(destination: LazyView(TrendingView()), tag: TabSelection.trending, selection: $navigation.tabSelection) {
                         Label("Trending", systemImage: "arrow.up.right.circle.fill")
                             .accessibility(label: Text("Trending"))

Shared/OpenURLHandler.swift

@@ -74,6 +74,7 @@ struct OpenURLHandler {
                 focusMainWindow()
             #endif
         case .trending:
+            guard FeatureFlags.trendingEnabled else { return }
             navigation.hideViewsAboveBrowser()
             navigation.tabSelection = .trending
             #if os(macOS)

Shared/Settings/BrowsingSettings.swift

@@ -258,11 +258,13 @@ struct BrowsingSettings: View {
     private var visibleSectionsSettings: some View {
         Section(header: SettingsHeader(text: "Sections".localized())) {
             ForEach(VisibleSection.allCases, id: \.self) { section in
-                MultiselectRow(
-                    title: section.title,
-                    selected: visibleSections.contains(section)
-                ) { value in
-                    toggleSection(section, value: value)
+                if section != .trending || FeatureFlags.trendingEnabled {
+                    MultiselectRow(
+                        title: section.title,
+                        selected: visibleSections.contains(section)
+                    ) { value in
+                        toggleSection(section, value: value)
+                    }
                 }
             }
         }
@@ -279,7 +281,9 @@ struct BrowsingSettings: View {
                     Spacer()
                     Picker("Startup section", selection: $startupSection) {
                         ForEach(StartupSection.allCases, id: \.rawValue) { section in
-                            Text(section.label).tag(section)
+                            if section != .trending || FeatureFlags.trendingEnabled {
+                                Text(section.label).tag(section)
+                            }
                         }
                     }
                     .modifier(SettingsPickerModifier())
@@ -287,7 +291,9 @@ struct BrowsingSettings: View {
             #else
                 Picker("Startup section", selection: $startupSection) {
                     ForEach(StartupSection.allCases, id: \.rawValue) { section in
-                        Text(section.label).tag(section)
+                        if section != .trending || FeatureFlags.trendingEnabled {
+                            Text(section.label).tag(section)
+                        }
                     }
                 }
                 .modifier(SettingsPickerModifier())