Task edition improvements (#9)

This PR contains the work done to improve upon the editing experience on the **Task list item and the **New task** views.

Reviewed-on: rock-n-code/todos-app#9
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

App/Sources/View Modifiers/OnEmptyNewlineResignFocusModifier.swift

@@ -0,0 +1,81 @@
+import SwiftUI
+
+/// A view modifier that clears text and removes focus when return is pressed on empty content.
+///
+/// This modifier monitors text changes and provides smart handling of newlines:
+/// - Empty text is allowed normally
+/// - Newlines at the end of whitespace-only text clear the field and remove focus
+/// - Multi-line content with actual text is preserved normally
+struct OnEmptyNewlineResignFocusModifier<Field: Hashable>: ViewModifier {
+
+    // MARK: Properties
+
+    /// Binding to the text being edited.
+    @Binding
+    private var text: String
+
+    /// Binding to the focus state.
+    private let focusState: FocusState<Field?>.Binding
+
+    // MARK: Initializers
+
+    /// Creates a modifier that clears text on empty newline.
+    ///
+    /// - Parameters:
+    ///   - text: A binding to the text being edited.
+    ///   - focusState: A binding to the focus state.
+    init(
+        text: Binding<String>,
+        focusState: FocusState<Field?>.Binding
+    ) {
+        self._text = text
+        self.focusState = focusState
+    }
+
+    // MARK: Body
+
+    /// The content and behavior of the view modifier.
+    func body(content: Content) -> some View {
+        content
+            .onChange(of: text) { oldValue, newValue in
+                guard newValue.isEmpty == false else {
+                    return
+                }
+
+                if newValue.last == .newline {
+                    if newValue.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty {
+                        text = ""
+                        focusState.wrappedValue = nil
+                    }
+                }
+            }
+    }
+
+}
+
+// MARK: - View Extension
+
+extension View {
+
+    /// Clears the text and removes focus when return is pressed on empty content.
+    ///
+    /// This modifier allows users to dismiss an optional text field by pressing return
+    /// when the field is empty or contains only whitespace. Multi-line content is preserved normally.
+    ///
+    /// - Parameters:
+    ///   - focusState: A binding to the focus state.
+    ///   - text: A binding to the text being edited.
+    /// - Returns: A modified view with clear-on-empty behavior.
+    func onEmptyNewlineResignFocus<Field: Hashable>(
+        text: Binding<String>,
+        from focusState: FocusState<Field?>.Binding
+    ) -> some View {
+        modifier(
+            OnEmptyNewlineResignFocusModifier(
+                text: text,
+                focusState: focusState
+            )
+        )
+    }
+
+}