Add RollkofferSimulator iOS SpriteKit arcade game

Complete implementation of a 2D top-down arcade collector game where players
control a rolling suitcase through an airport, collecting good dogs and green
people while avoiding bad dogs and gray people.

Features:
- Touch & drag controls for suitcase movement
- Automatic scrolling airport floor with tile pattern
- 4 entity types: good dogs (small/big), bad dogs, green/gray humans
- Spawn system with configurable distribution rates
- Collision detection with visual feedback effects
- Score tracking with high score persistence
- 90-second time limit with 10 dogs + 5 humans goal
- 3 lives system with invincibility frames
- Menu, Game, GameOver, and Victory scenes
- German UI text (Created by Ingo K.)

Technical:
- iOS 15+ with SpriteKit framework
- Modular architecture with Nodes, Managers, Scenes
- Physics-based collision detection
- UserDefaults for score persistence

RollkofferSimulator/Managers/SpawnManager.swift

@@ -0,0 +1,104 @@
+//
+//  SpawnManager.swift
+//  RollkofferSimulator
+//
+//  Created by Ingo K.
+//
+
+import SpriteKit
+
+/// Manages spawning of entities at the top of the screen
+class SpawnManager {
+
+    // MARK: - Properties
+    private weak var scene: SKScene?
+    private var spawnTimer: TimeInterval = 0
+    private var nextSpawnInterval: TimeInterval = 0
+    private var isSpawning: Bool = false
+
+    // MARK: - Initialization
+    init(scene: SKScene) {
+        self.scene = scene
+        resetSpawnInterval()
+    }
+
+    // MARK: - Public Methods
+    func startSpawning() {
+        isSpawning = true
+        resetSpawnInterval()
+    }
+
+    func stopSpawning() {
+        isSpawning = false
+    }
+
+    func update(deltaTime: TimeInterval) {
+        guard isSpawning else { return }
+
+        spawnTimer += deltaTime
+
+        if spawnTimer >= nextSpawnInterval {
+            spawnEntity()
+            spawnTimer = 0
+            resetSpawnInterval()
+        }
+    }
+
+    // MARK: - Private Methods
+    private func resetSpawnInterval() {
+        nextSpawnInterval = TimeInterval.random(in: Constants.spawnIntervalMin...Constants.spawnIntervalMax)
+    }
+
+    private func spawnEntity() {
+        guard let scene = scene else { return }
+
+        let entityType = determineEntityType()
+        let entity = createEntity(type: entityType)
+
+        // Random x position
+        let margin: CGFloat = 60
+        let minX = margin
+        let maxX = scene.frame.width - margin
+        let randomX = CGFloat.random(in: minX...maxX)
+
+        // Spawn above screen
+        entity.position = CGPoint(x: randomX, y: scene.frame.height + 50)
+
+        scene.addChild(entity)
+
+        // Move entity down
+        let moveDistance = scene.frame.height + 200
+        let moveDuration = moveDistance / Constants.scrollSpeed
+        let moveAction = SKAction.moveBy(x: 0, y: -moveDistance, duration: moveDuration)
+        let removeAction = SKAction.removeFromParent()
+        entity.run(SKAction.sequence([moveAction, removeAction]))
+    }
+
+    private func determineEntityType() -> EntityType {
+        let roll = Int.random(in: 0..<100)
+
+        if roll < Constants.spawnChanceGoodDog {
+            // 40% good dogs (split between small and big)
+            let isSmall = Bool.random()
+            return .dog(isSmall ? .smallGood : .bigGood)
+        } else if roll < Constants.spawnChanceBadDog {
+            // 20% bad dogs
+            return .dog(.bad)
+        } else if roll < Constants.spawnChanceGreenHuman {
+            // 25% green humans
+            return .human(.green)
+        } else {
+            // 15% gray humans
+            return .human(.gray)
+        }
+    }
+
+    private func createEntity(type: EntityType) -> SKNode {
+        switch type {
+        case .dog(let dogType):
+            return DogNode(type: dogType)
+        case .human(let humanType):
+            return HumanNode(type: humanType)
+        }
+    }
+}