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

auth.go

@@ -178,6 +178,10 @@ func isValidPassword(password string) bool { // Validate password complexity and
 }
 
 func ValidateTimeStamp(header http.Header) bool {
+	if isDebug {
+		return true
+	}
+
 	timeStampStr := header.Get("X-Timestamp")
 	if timeStampStr == "" {
 		return false
@@ -188,10 +192,6 @@ func ValidateTimeStamp(header http.Header) bool {
 		return false
 	}
 
-	if globalConfig.Debug {
-		return true
-	}
-
 	currentTime := time.Now().UnixMilli()
 	if currentTime-timeStamp > 3000 || timeStamp-currentTime > 3000 {
 		return false