feat: home screen quick actions (long press app icon)

Adds four UIApplicationShortcutItems registered dynamically at launch:
  • Add Task — opens the add-task sheet immediately, any tab
  • Today — switches to the Today tab
  • Calendar — switches to the Calendar tab
  • Workout — switches to the Workout tab (only registered if the
    workout tab is enabled in settings; re-registers when the setting changes)

Cold-launch and foreground-activation paths both handled via AppDelegate.
ShortcutHandler singleton bridges UIKit callbacks to SwiftUI via @Published.

KisaniCal/ContentView.swift

@@ -9,9 +9,11 @@ struct ContentView: View {
     @AppStorage("showMatrixTab")   private var showMatrixTab   = true
     @AppStorage("showWorkoutTab")  private var showWorkoutTab  = true
     @AppStorage("hasOnboarded")    private var hasOnboarded    = false
-    @State private var showOnboarding = false
-    @State private var selectedTab    = 0
-    @StateObject private var tabState  = FloatingTabState()
+    @State private var showOnboarding    = false
+    @State private var selectedTab       = 0
+    @State private var showQuickAddTask  = false
+    @StateObject private var tabState    = FloatingTabState()
+    @ObservedObject private var shortcuts = ShortcutHandler.shared
     @State private var iPadSelection: Int? = 0
     @State private var calIconImage: Image = ContentView.buildCalIcon()
 
@@ -92,6 +94,27 @@ struct ContentView: View {
         .onChange(of: workoutVM.doneSets) { _ in
             NotificationManager.shared.reschedule(workoutVM: workoutVM, taskVM: taskVM)
         }
+        .onChange(of: shortcuts.pending) { action in
+            guard let action else { return }
+            switch action {
+            case .addTask:
+                showQuickAddTask = true
+            case .today:
+                withAnimation(KisaniSpring.micro) { selectedTab = 0 }
+            case .calendar:
+                withAnimation(KisaniSpring.micro) { selectedTab = 1 }
+            case .workout:
+                withAnimation(KisaniSpring.micro) { selectedTab = showWorkoutTab ? 3 : 0 }
+            }
+            shortcuts.consume()
+        }
+        .sheet(isPresented: $showQuickAddTask) {
+            AddTaskSheet(prefilledDate: Date())
+                .environmentObject(taskVM)
+                .presentationDetents([.height(150)])
+                .presentationDragIndicator(.visible)
+        }
+        .onChange(of: showWorkoutTab) { _ in ShortcutHandler.registerShortcuts() }
     }
 
     // MARK: - iPhone