feat(macos): add native menu bar app with notch overlay

Introduces a SwiftUI companion app for the Fail Well PWA: menu bar
status item, popover with task list / record / history views, command
palette, and a Dynamic Island-style notch overlay that shows the active
step and timer beside the hardware notch and expands on hover to reveal
pause/next controls.

macos/Sources/FailWell/Services/Clock.swift

@@ -0,0 +1,25 @@
+import Foundation
+import Observation
+
+@MainActor
+@Observable
+final class Clock {
+    var now: Date = Date()
+
+    @ObservationIgnored private var tickTask: Task<Void, Never>?
+
+    init(tickInterval: Duration = .milliseconds(500)) {
+        tickTask = Task { [weak self] in
+            while !Task.isCancelled {
+                await MainActor.run {
+                    self?.now = Date()
+                }
+                try? await Task.sleep(for: tickInterval)
+            }
+        }
+    }
+
+    deinit {
+        tickTask?.cancel()
+    }
+}