Maintenance: ImageUtils - Eliminate unnecessary HTTP request and improve performance (#121)

Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.5 <[email protected]>

Author: 3 people

src/main/java/spring/memewikibe/common/util/ImageUtils.java

@@ -47,30 +47,11 @@ public static byte[] downloadBytes(String url) throws IOException {
     }
 
     public static String detectMimeType(String imageUrl, byte[] data) {
-        // Try by HTTP response header
-        try {
-            URI uri = new URI(imageUrl);
-            HttpRequest request = HttpRequest.newBuilder()
-                .uri(uri)
-                .timeout(Duration.ofSeconds(5))
-                .method("HEAD", HttpRequest.BodyPublishers.noBody())
-                .build();
-            
-            HttpResponse<Void> response = HTTP_CLIENT.send(request, HttpResponse.BodyHandlers.discarding());
-            String contentType = response.headers().firstValue("Content-Type").orElse(null);
-            if (StringUtils.hasText(contentType)) {
-                // Content-Type might include charset, so extract only the MIME type
-                return contentType.split(";")[0].trim();
-            }
-        } catch (Exception ignored) {
-            // If HEAD request fails, continue with other methods
-        }
-        
-        // Try by stream content sniffing using legacy method (still works for content detection)
+        // Prioritize byte signature analysis (fastest and most reliable)
         String guessed = guessContentTypeFromBytes(data);
         if (StringUtils.hasText(guessed)) return guessed;
-        
-        // Fallback by extension
+
+        // Fallback to extension-based detection
         return getMimeTypeByExtension(imageUrl);
     }
 

src/test/java/spring/memewikibe/common/util/ZsetConcurrencyTest.java

@@ -106,8 +106,6 @@ void zset_is_not_thread_safe_mixed_operations() throws InterruptedException {
 
         // 이 assertion은 자주 실패함 (내부 일관성이 깨짐을 증명)
         // dictSize와 skipSize가 다를 수 있음
-        System.out.println("Dict size: " + dictSize + ", Skip size: " + skipSize);
-
         // 최소한 하나 이상의 데이터가 있어야 함
         then(dictSize + skipSize).isGreaterThan(0);
     }