add simulator mode to desktop designer for testing apps

- Add --simulator flag to launch home screen showing discovered apps
- Create app discovery system to scan test-apps/ directory
- Build simulator home screen with dark phone-like UI
- Add Lua API: simulator.launchApp, simulator.goHome, simulator.getApps
- ESC key returns to home when inside an app
- Apps displayed with icons in grid layout

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

designer/src/app_discovery.h

@@ -0,0 +1,32 @@
+// D:\Dev\Mosis\MosisService\designer\src\app_discovery.h
+#pragma once
+
+#include <string>
+#include <vector>
+
+namespace mosis {
+
+struct AppInfo {
+    std::string id;           // e.g., "com.mosis.sandbox-test"
+    std::string name;         // Display name
+    std::string version;      // Version string
+    std::string entry;        // Entry point (e.g., "main.rml")
+    std::string icon;         // Icon filename (e.g., "icon.tga")
+    std::string description;  // App description
+    std::string app_path;     // Full path to app directory
+
+    // Computed paths
+    std::string GetEntryPath() const { return app_path + "/" + entry; }
+    std::string GetIconPath() const { return app_path + "/" + icon; }
+};
+
+class AppDiscovery {
+public:
+    // Scan a directory for apps (folders with manifest.json)
+    static std::vector<AppInfo> DiscoverApps(const std::string& apps_directory);
+
+    // Load a single app's manifest
+    static bool LoadAppManifest(const std::string& app_directory, AppInfo& info);
+};
+
+} // namespace mosis