⚡ Bolt: HexFormat를 사용한 16진수 문자열 변환 성능 최적화

src/main/java/com/clearfolio/viewer/artifact/ArtifactLinkService.java

@@ -423,11 +423,8 @@ private static String sha256Hex(byte[] bytes) {
         try {
             MessageDigest digest = MessageDigest.getInstance("SHA-256");
             byte[] raw = digest.digest(bytes);
-            StringBuilder hex = new StringBuilder(raw.length * 2);
-            for (byte b : raw) {
-                hex.append(String.format("%02x", b));
-            }
-            return hex.toString();
+            // Bolt: Using HexFormat for faster byte-to-hex conversion instead of String.format inside a loop.
+            return java.util.HexFormat.of().formatHex(raw);
         } catch (GeneralSecurityException ex) {
             throw new IllegalStateException("SHA-256 digest unavailable", ex);
         }

src/main/java/com/clearfolio/viewer/service/DefaultDocumentConversionService.java

@@ -160,12 +160,8 @@ private String contentHash(MultipartFile file) {
             }
 
             byte[] raw = digest.digest();
-            StringBuilder hex = new StringBuilder(raw.length * 2);
-            for (byte b : raw) {
-                hex.append(String.format("%02x", b));
-            }
-
-            return hex.toString();
+            // Bolt: Using HexFormat for faster byte-to-hex conversion instead of String.format inside a loop.
+            return java.util.HexFormat.of().formatHex(raw);
         } catch (NoSuchAlgorithmException ex) {
             throw new IllegalStateException("SHA-256 digest unavailable", ex);
         } catch (IOException ex) {