refactor: consolidate debug flag and update gitignore

- Rename debugMode to isDebug for consistency across codebase
- Move debug flag check in ValidateTimeStamp to match other validations
- Add database.db to gitignore and remove unused config file
- Update README.md to clarify user registration rules

README.md

@@ -92,8 +92,7 @@ X-Timestamp: 1704067200000
 ```json
 {
   "username": "your_username",
-  "passwd": "YourPass123!",
-  "type": "admin"
+  "passwd": "YourPass123!"
 }
 ```
 
@@ -119,6 +118,7 @@ X-Timestamp: 1704067200000
   }
 }
 ```
+> New user only can register as visitor, superuser and admin need to contact the administrator to apply.
 
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