[Feat] Add Base64 decoding logic for autoCompleteCongestionMessage in ClovaPromptProperties.java

Author: KOKEONHO

src/main/java/boombimapi/global/properties/ClovaPromptProperties.java

@@ -1,10 +1,22 @@
 package boombimapi.global.properties;
 
+import java.nio.charset.StandardCharsets;
+import java.util.Base64;
 import org.springframework.boot.context.properties.ConfigurationProperties;
 
 @ConfigurationProperties(prefix = "clova.prompts")
 public record ClovaPromptProperties(
     String autoCompleteCongestionMessage
 ) {
 
+    public String autoCompleteCongestionMessage() {
+        if (autoCompleteCongestionMessage == null || autoCompleteCongestionMessage.isBlank()) {
+            return "";
+        }
+        // 혹시 공백/개행 들어오면 제거
+        String compact = autoCompleteCongestionMessage.replaceAll("\\s+", "");
+        byte[] decoded = Base64.getDecoder().decode(compact);
+        return new String(decoded, StandardCharsets.UTF_8);
+    }
+
 }