Replaces all usages of JsonSerializer.Serialize with the UnsafeRelaxed option via a new JsonOptions.UnsafeRelaxed static property. This ensures consistent relaxed escaping for all JSON output, improving compatibility with consumers expecting unescaped JSON. Refactors affected command, service, and static classes to use the new option.
Wraps InventoryUpdateEvent logic in a Task to run asynchronously, improving responsiveness and preventing blocking of the main thread during event processing.
Migrated all serialization and deserialization from Newtonsoft.Json to System.Text.Json across the codebase for improved performance and reduced dependencies. Updated package references and refactored helper method names for consistency (e.g., IsEmpty, NotEmpty, InRange). Also updated NuGet package versions in project files.
