Add Tonuino Manager website and Sparkle updates

Sources/TonuinoManager/App/ContentView.swift

@@ -0,0 +1,53 @@
+import SwiftUI
+
+struct ContentView: View {
+    @EnvironmentObject private var app: AppModel
+
+    var body: some View {
+        VStack(spacing: 0) {
+            NavigationSplitView {
+                List(AppModel.Section.allCases, selection: $app.section) { item in
+                    Label(item.rawValue, systemImage: item.icon).tag(item)
+                }
+                .listStyle(.sidebar)
+                .navigationTitle("Tonuino Manager")
+                .safeAreaInset(edge: .bottom) {
+                    HStack(spacing: 8) {
+                        Circle().fill(app.library.rootURL == nil ? Color.secondary : Color.green).frame(width: 8, height: 8)
+                        Text(app.library.activeProfile.map { "Lokal · \($0.name)" } ?? (app.library.rootURL?.lastPathComponent ?? "Keine Bibliothek ausgewählt"))
+                            .lineLimit(1).foregroundStyle(.secondary)
+                    }
+                    .font(.caption).padding()
+                }
+            } detail: {
+                switch app.section {
+                case .library: LibraryView()
+                case .cards: CardsView()
+                case .tonuino: TonuinoSettingsView()
+                case .settings: SettingsView()
+                }
+            }
+            .frame(maxWidth: .infinity, maxHeight: .infinity)
+
+            HStack {
+                Spacer(minLength: 0)
+                Text(app.status)
+                    .font(.caption)
+                    .foregroundStyle(.secondary)
+                    .lineLimit(1)
+                    .truncationMode(.tail)
+                    .frame(maxWidth: 520, alignment: .trailing)
+            }
+            .padding(.horizontal, 14)
+            .padding(.vertical, 6)
+            .frame(maxWidth: .infinity)
+            .background(.regularMaterial)
+            .overlay(alignment: .top) {
+                Rectangle().fill(.primary.opacity(0.08)).frame(height: 1)
+            }
+        }
+        .alert("Fehler", isPresented: $app.showError) {
+            Button("OK", role: .cancel) { }
+        } message: { Text(app.errorMessage ?? "Unbekannter Fehler") }
+    }
+}