fix(layout): fix rotation crash and improve iPad split view

iPadLayout was rendering TodayView without workoutVM, crashing with
a fatal EnvironmentObject error on any device where hSizeClass goes
.regular (iPad, iPhone Plus/Max in landscape). Rewrote to use proper
NavigationSplitView with List(selection:) driving the detail column.

Also caches calendarIcon as a static func + @State instead of
recomputing UIGraphicsImageRenderer on every body evaluation.

KisaniCal/ContentView.swift

@@ -11,8 +11,10 @@ struct ContentView: View {
     @AppStorage("hasOnboarded")    private var hasOnboarded    = false
     @State private var showOnboarding = false
     @State private var selectedTab    = 0
+    @State private var iPadSelection: Int? = 0
+    @State private var calIconImage: Image = ContentView.buildCalIcon()
 
-    private var calendarIcon: Image {
+    private static func buildCalIcon() -> Image {
         let day = Calendar.current.component(.day, from: Date())
         let size = CGSize(width: 26, height: 26)
         let renderer = UIGraphicsImageRenderer(size: size)
@@ -21,14 +23,12 @@ struct ContentView: View {
             let lw: CGFloat = 1.5
             let cr: CGFloat = 4.5
 
-            // Outer rounded rectangle body
             let body = CGRect(x: lw / 2, y: 3, width: size.width - lw, height: size.height - 3 - lw / 2)
             let bodyPath = UIBezierPath(roundedRect: body, cornerRadius: cr)
             color.setStroke()
             bodyPath.lineWidth = lw
             bodyPath.stroke()
 
-            // Header divider line
             let divY = body.minY + 7.5
             let divPath = UIBezierPath()
             divPath.move(to: CGPoint(x: body.minX + lw / 2, y: divY))
@@ -37,13 +37,11 @@ struct ContentView: View {
             divPath.lineWidth = 1
             divPath.stroke()
 
-            // Ring bumps at top
             color.setFill()
             for rx in [size.width * 0.3, size.width * 0.7] {
                 UIBezierPath(roundedRect: CGRect(x: rx - 1.5, y: 0.5, width: 3, height: 5.5), cornerRadius: 1.5).fill()
             }
 
-            // Date number centred in body below header
             let s = "\(day)"
             let font = UIFont.systemFont(ofSize: floor(size.height * 0.38), weight: .bold)
             let attrs: [NSAttributedString.Key: Any] = [.font: font, .foregroundColor: color]
@@ -133,7 +131,7 @@ struct ContentView: View {
 
             KisaniTabBar(
                 selection: $selectedTab,
-                calIcon: calendarIcon,
+                calIcon: calIconImage,
                 showMatrix: showMatrixTab,
                 showWorkout: showWorkoutTab
             )
@@ -146,42 +144,27 @@ struct ContentView: View {
     // MARK: - iPad
     @ViewBuilder
     private func iPadLayout() -> some View {
-        NavigationSplitView(columnVisibility: .constant(.all)) {
-            List {
-                iPadSidebarItem("Tasks",    icon: "checkmark",       tag: 0)
-                iPadSidebarItem("Calendar", icon: "calendar",        tag: 1)
-                if showMatrixTab {
-                    iPadSidebarItem("Matrix", icon: "square.grid.2x2", tag: 2)
-                }
-                if showWorkoutTab {
-                    iPadSidebarItem("Workout", icon: "dumbbell",      tag: 3)
-                }
-                iPadSidebarItem("Settings", icon: "gearshape",       tag: 4)
+        NavigationSplitView {
+            List(selection: $iPadSelection) {
+                Label("Tasks",    systemImage: "checkmark").tag(0)
+                Label("Calendar", systemImage: "calendar").tag(1)
+                if showMatrixTab  { Label("Matrix",   systemImage: "square.grid.2x2").tag(2) }
+                if showWorkoutTab { Label("Workout",  systemImage: "dumbbell").tag(3) }
+                Label("Settings", systemImage: "gearshape").tag(4)
             }
             .navigationTitle("Kisani Cal")
             .listStyle(.sidebar)
         } detail: {
-            TodayView().environmentObject(taskVM)
-        }
-        .tint(AppColors.accent)
-    }
-
-    private func iPadSidebarItem(_ label: String, icon: String, tag: Int) -> some View {
-        NavigationLink(destination: iPadDetail(tag: tag)) {
-            Label(label, systemImage: icon)
-        }
-    }
-
-    @ViewBuilder
-    private func iPadDetail(tag: Int) -> some View {
-        switch tag {
-        case 0: TodayView().environmentObject(taskVM).environmentObject(workoutVM)
+            switch iPadSelection ?? 0 {
             case 1:  CalendarView().environmentObject(taskVM).environmentObject(workoutVM)
             case 2:  MatrixView().environmentObject(taskVM)
             case 3:  WorkoutView().environmentObject(workoutVM)
-        default: SettingsView().environmentObject(workoutVM)
+            case 4:  SettingsView().environmentObject(workoutVM)
+            default: TodayView().environmentObject(taskVM).environmentObject(workoutVM)
             }
         }
+        .tint(AppColors.accent)
+    }
 }
 
 // MARK: - Custom Tab Bar