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.

constant/midjourney.go

@@ -1,11 +1,5 @@
 package constant
 
-var MjNotifyEnabled = false
-var MjAccountFilterEnabled = false
-var MjModeClearEnabled = false
-var MjForwardUrlEnabled = true
-var MjActionCheckSuccessEnabled = true
-
 const (
 	MjErrorUnknown = 5
 	MjRequestError = 4