extract shared mosis-core library from sandbox APIs

Create core/ directory with platform-agnostic sandbox components:
- Timer manager, JSON API, Crypto API, Virtual FS
- Lua sandbox, Permission gate, Audit log, Rate limiter
- Platform abstraction interfaces (IAssetInterface, IFilesystemInterface)
- Platform-agnostic logger with Android/Desktop implementations

Update designer to link against mosis-core library instead of
including sandbox sources directly.

This is the foundation for unifying the Android service and
desktop designer to share the same codebase.

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

core/include/mosis/apps/app_api.h

@@ -0,0 +1,23 @@
+// app_api.h - Lua API bindings for app management
+// Milestone 10: Device-Side App Management
+#pragma once
+
+#include <string>
+
+struct lua_State;
+
+namespace mosis {
+
+class AppManager;
+class UpdateService;
+
+// Register Lua APIs for app management
+// - mosis.apps.* - System apps only (App Store, Settings)
+// - mosis.app.* - All apps (info about current app)
+void RegisterAppAPIs(lua_State* L,
+                     AppManager* app_manager,
+                     UpdateService* update_service,
+                     const std::string& current_app_id,
+                     bool is_system_app);
+
+} // namespace mosis