ui: Fixes for iOS 26 toolbars

Note: This will only become user-facing once we switch to liquid glass
mode, therefore no changelog entry is needed now.

Changelog-None
Closes: https://github.com/damus-io/damus/issues/3702
Co-Authored-by: Daniel D’Aquino <daniel@daquino.me>
Signed-off-by: ericholguin <ericholguin@apache.org>

damus/ContentView.swift

@@ -254,6 +254,7 @@ struct ContentView: View {
                                 ToolbarItem(placement: .navigationBarLeading) {
                                     TopbarSideMenuButton(damus_state: damus, isSideBarOpened: $isSideBarOpened)
                                 }
+                                .hideToolbarBackground()
                                 
                                 ToolbarItem(placement: .navigationBarTrailing) {
                                     HStack(alignment: .center) {
@@ -271,6 +272,7 @@ struct ContentView: View {
                                         }
                                     }
                                 }
+                                .hideToolbarBackground()
                             }
                     }
                     .background(DamusColors.adaptableWhite)

damus/Features/Notifications/Views/NotificationsView.swift

@@ -124,6 +124,8 @@ struct NotificationsView: View {
                     }
                 )
             }
+            .hideToolbarBackground()
+            
             ToolbarItem(placement: .navigationBarTrailing) {
                 if showTrustedButton {
                     TrustedNetworkButton(filter: $filter.friend_filter) {
@@ -133,6 +135,7 @@ struct NotificationsView: View {
                     }
                 }
             }
+            .hideToolbarBackground()
         }
         .onChange(of: filter.friend_filter) { val in
             state.settings.friend_filter = val

damus/Features/Profile/Views/ProfileView.swift

@@ -503,6 +503,8 @@ struct ProfileView: View {
                         .padding(.top, max(5, 15 + (yOffset / 30)))
                     }
                 }
+                .hideToolbarBackground()
+                
                 if showFollowBtnInBlurrBanner() {
                     ToolbarItem(placement: .topBarTrailing) {
                         FollowButtonView(
@@ -512,12 +514,14 @@ struct ProfileView: View {
                         )
                         .padding(.top, 8)
                     }
+                    .hideToolbarBackground()
                 } else {
                     ToolbarItem(placement: .topBarTrailing) {
                         navActionSheetButton
                             .padding(.top, 5)
                             .accentColor(DamusColors.white)
                     }
+                    .hideToolbarBackground()
                 }
             }
             .toolbarBackground(.hidden)

damus/Shared/Modifiers/ToolbarItemModifier.swift

@@ -0,0 +1,35 @@
+//
+//  ToolbarItemModifier.swift
+//  damus
+//
+
+import SwiftUI
+
+/// Extension that adds the `.hideToolbarBackground()` modifier to toolbar content.
+///
+/// This modifier conditionally applies `.sharedBackgroundVisibility(.hidden)` on iOS 26+,
+/// eliminating the need for duplicated `if #available(iOS 26.0, *)` checks throughout the codebase.
+///
+/// - Usage:
+///   ```swift
+///   .toolbar {
+///       ToolbarItem(placement: .navigationBarLeading) {
+///           Button("Action") { }
+///       }
+///       .hideToolbarBackground()
+///   }
+///   ```
+@available(iOS 15.0, *)
+extension ToolbarContent {
+    /// Hides the toolbar background on iOS 26+, leaving it unchanged on earlier versions.
+    ///
+    /// Apply this modifier to `ToolbarItem` views to suppress the shared background
+    /// visibility introduced in iOS 26 without duplicating version checks.
+    func hideToolbarBackground() -> some ToolbarContent {
+        if #available(iOS 26.0, *) {
+            return self.sharedBackgroundVisibility(.hidden)
+        } else {
+            return self
+        }
+    }
+}