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/util/logger.h

@@ -0,0 +1,40 @@
+#pragma once
+#include <string>
+#include <cstdio>
+#include <cstdarg>
+
+class Logger
+{
+public:
+    static void Log(const std::string& message);
+
+    // Printf-style logging
+    static void LogF(const char* level, const char* fmt, ...) {
+        char buffer[1024];
+        va_list args;
+        va_start(args, fmt);
+        vsnprintf(buffer, sizeof(buffer), fmt, args);
+        va_end(args);
+        Log(std::string("[") + level + "] " + buffer);
+    }
+};
+
+// Undefine conflicting syslog macros if present
+#ifdef LOG_DEBUG
+#undef LOG_DEBUG
+#endif
+#ifdef LOG_INFO
+#undef LOG_INFO
+#endif
+#ifdef LOG_WARN
+#undef LOG_WARN
+#endif
+#ifdef LOG_ERROR
+#undef LOG_ERROR
+#endif
+
+// Logging macros for convenience (printf-style)
+#define LOG_DEBUG(fmt, ...) Logger::LogF("DEBUG", fmt __VA_OPT__(,) __VA_ARGS__)
+#define LOG_INFO(fmt, ...) Logger::LogF("INFO", fmt __VA_OPT__(,) __VA_ARGS__)
+#define LOG_WARN(fmt, ...) Logger::LogF("WARN", fmt __VA_OPT__(,) __VA_ARGS__)
+#define LOG_ERROR(fmt, ...) Logger::LogF("ERROR", fmt __VA_OPT__(,) __VA_ARGS__)