feat(util): JsonUtil.normalizeEvaluation — 평문→JSON 래핑 + 300자 제한

- evaluation 컬럼이 IS JSON 제약이라 평문은 {"text":"..."}로 정규화
- parseMap이 잘못된 JSON 받았을 때 빈 Map 대신 {"text":원문}으로 보존
- PipelineService/RestaurantService에서 이미 호출 중인 유틸 — 미커밋 상태였음

🤖 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/util/JsonUtil.java

@@ -53,7 +53,8 @@ public final class JsonUtil {
         try {
             return MAPPER.readValue(json, new TypeReference<>() {});
         } catch (Exception e) {
-            return Collections.emptyMap();
+            // Plain text or malformed JSON (e.g. Python-style single quotes) → wrap as {"text": "..."}
+            return Map.of("text", json.trim());
         }
     }
 
@@ -74,6 +75,24 @@ public final class JsonUtil {
         return rows.stream().map(JsonUtil::lowerKeys).collect(Collectors.toList());
     }
 
+    /**
+     * Normalize evaluation to a valid JSON object string (e.g. {"text":"..."}).
+     * Plain text is wrapped, already-valid JSON is returned as-is, and text is truncated to maxLen.
+     */
+    public static String normalizeEvaluation(String eval, int maxLen) {
+        if (eval == null || eval.isBlank()) return null;
+        String trimmed = eval.trim();
+        if (trimmed.startsWith("{")) return trimmed;
+        if (trimmed.length() > maxLen) {
+            trimmed = trimmed.substring(0, maxLen);
+        }
+        return toJson(Map.of("text", trimmed));
+    }
+
+    public static String normalizeEvaluation(String eval) {
+        return normalizeEvaluation(eval, 300);
+    }
+
     public static String toJson(Object value) {
         try {
             return MAPPER.writeValueAsString(value);