Fix iPad iOS 18 keyboard dismissal issue in search

Removed auto-focus logic that was causing keyboard show/hide loop
on iPad with docked keyboard. The keyboard was repeatedly dismissing
immediately after appearing due to interaction between keyboard
notifications, focus state changes, and view updates.

Changes:
- Removed focused state and keyboard observer from SearchModel
- Removed iOS textField reference (kept macOS only)
- Removed auto-focus logic from FocusableSearchTextField on iOS
- Cleaned up unused focus-related code

The search field now works reliably when tapped manually on iPad.
Auto-focus still works on macOS where it doesn't cause issues.

Model/NavigationModel.swift

@@ -318,7 +318,7 @@ final class NavigationModel: ObservableObject {
     func multipleTapHandler() {
         switch tabSelection {
         case .search:
-            search.focused = true
+            break
         default:
             print("not implemented")
         }

Model/Search/SearchModel.swift

@@ -16,13 +16,9 @@ final class SearchModel: ObservableObject {
     @Published var querySuggestions = [String]()
     private var suggestionsDebouncer = Debouncer(.milliseconds(200))
 
-    @Published var focused = false
-
     @Default(.showSearchSuggestions) private var showSearchSuggestions
 
-    #if os(iOS)
-        var textField: UITextField!
-    #elseif os(macOS)
+    #if os(macOS)
         var textField: NSTextField!
     #endif
 
@@ -30,15 +26,9 @@ final class SearchModel: ObservableObject {
     private var resource: Resource!
 
     init() {
-        #if os(iOS)
-            addKeyboardDidHideNotificationObserver()
-        #endif
     }
 
     deinit {
-        #if os(iOS)
-            removeKeyboardDidHideNotificationObserver()
-        #endif
     }
 
     var isLoading: Bool {
@@ -158,18 +148,4 @@ final class SearchModel: ObservableObject {
                 }
             }
     }
-
-    #if os(iOS)
-        private func addKeyboardDidHideNotificationObserver() {
-            NotificationCenter.default.addObserver(self, selector: #selector(onKeyboardDidHide), name: UIResponder.keyboardDidHideNotification, object: nil)
-        }
-
-        @objc func onKeyboardDidHide() {
-            focused = false
-        }
-
-        private func removeKeyboardDidHideNotificationObserver() {
-            NotificationCenter.default.removeObserver(self, name: UIResponder.keyboardDidHideNotification, object: nil)
-        }
-    #endif
 }