Add HealthBridge iOS app for intelligent health data synchronization

Complete implementation of a SwiftUI iOS app that serves as a "Single Source
of Truth" for health data. The app reads from all Apple Health sources,
detects conflicts between devices, merges data using configurable strategies,
and writes cleaned data back.

Features:
- Phase 1: HealthKit integration with automatic source discovery
- Phase 2: DataReader with conflict detection (time-window based)
- Phase 3: RuleEngine with 8 merge strategies (exclusive, priority, higher wins, etc.)
- Phase 4: MergeEngine for conflict resolution + DataWriter for HealthKit writes
- Phase 5: SwiftUI UI for dashboard, conflicts, rules, and sources management
- Phase 6: Background sync with configurable intervals and push notifications
- Phase 7: Complete rule editor and polished UI components

Supported data types:
- Steps, Heart Rate, Blood Pressure, SpO2, Sleep
- Distance, Floors Climbed, Active Energy, HRV, Respiratory Rate

Architecture: SourceManager -> DataReader -> RuleEngine -> MergeEngine -> DataWriter

HealthBridge/Views/ContentView.swift

@@ -0,0 +1,42 @@
+import SwiftUI
+
+struct ContentView: View {
+    @EnvironmentObject var appState: AppState
+    @EnvironmentObject var syncCoordinator: SyncCoordinator
+
+    var body: some View {
+        TabView(selection: $appState.selectedTab) {
+            DashboardView()
+                .tabItem {
+                    Label("Dashboard", systemImage: "chart.bar.fill")
+                }
+                .tag(AppState.Tab.dashboard)
+
+            ConflictsView()
+                .tabItem {
+                    Label("Konflikte", systemImage: "arrow.triangle.2.circlepath")
+                }
+                .tag(AppState.Tab.conflicts)
+                .badge(syncCoordinator.pendingConflicts.count)
+
+            RulesView()
+                .tabItem {
+                    Label("Regeln", systemImage: "slider.horizontal.3")
+                }
+                .tag(AppState.Tab.rules)
+
+            SourcesView()
+                .tabItem {
+                    Label("Quellen", systemImage: "antenna.radiowaves.left.and.right")
+                }
+                .tag(AppState.Tab.sources)
+        }
+        .tint(.blue)
+    }
+}
+
+#Preview {
+    ContentView()
+        .environmentObject(AppState())
+        .environmentObject(SyncCoordinator.shared)
+}