feat: Introduce settings package and refactor constants

- Added a new `setting` package to replace the `constant` package for configuration management, improving code organization and clarity.
- Moved various configuration variables such as `ServerAddress`, `PayAddress`, and `SensitiveWords` to the new `setting` package.
- Updated references throughout the codebase to use the new `setting` package, ensuring consistent access to configuration values.
- Introduced new files for managing chat settings and midjourney settings, enhancing modularity and maintainability of the code.

setting/system-setting.go

@@ -0,0 +1,9 @@
+package setting
+
+var ServerAddress = "http://localhost:3000"
+var WorkerUrl = ""
+var WorkerValidKey = ""
+
+func EnableWorker() bool {
+	return WorkerUrl != ""
+}