fix(search): WebSearchService HTTP timeout 추가 (connect 5s, request 15s)

- 특정 검색에서 무한 hang → backend virtual thread 점유로 후속 벌크 작업 중단
- Naver/DDG 둘 다 timeout 적용
- 타임아웃 시 HttpTimeoutException → 호출자(bulk)에서 notfound 안전 처리

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend-java/src/main/java/com/tasteby/service/WebSearchService.java

@@ -14,6 +14,7 @@ import java.net.http.HttpClient;
 import java.net.http.HttpRequest;
 import java.net.http.HttpResponse;
 import java.nio.charset.StandardCharsets;
+import java.time.Duration;
 import java.util.*;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -30,8 +31,10 @@ public class WebSearchService {
     private static final Logger log = LoggerFactory.getLogger(WebSearchService.class);
     private static final int MAX_RESULTS = 5;
 
+    private static final Duration REQ_TIMEOUT = Duration.ofSeconds(15);
     private static final HttpClient HTTP = HttpClient.newBuilder()
             .followRedirects(HttpClient.Redirect.NORMAL)
+            .connectTimeout(Duration.ofSeconds(5))
             .build();
 
     private static final Pattern DDG_RESULT = Pattern.compile(
@@ -74,6 +77,7 @@ public class WebSearchService {
         String url = "https://openapi.naver.com/v1/search/webkr.json?query=" + encoded + "&display=30";
         HttpRequest req = HttpRequest.newBuilder()
                 .uri(URI.create(url))
+                .timeout(REQ_TIMEOUT)
                 .header("X-Naver-Client-Id", naverClientId)
                 .header("X-Naver-Client-Secret", naverClientSecret)
                 .GET()
@@ -104,6 +108,7 @@ public class WebSearchService {
         String url = "https://html.duckduckgo.com/html/?q=" + encoded;
         HttpRequest req = HttpRequest.newBuilder()
                 .uri(URI.create(url))
+                .timeout(REQ_TIMEOUT)
                 .header("User-Agent", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36")
                 .header("Accept", "text/html,application/xhtml+xml")
                 .header("Accept-Language", "ko-KR,ko;q=0.9")