fix(library): library-neighbors JSONB cast 오류 — EXISTS 서브쿼리로 교체

app/api/documents.py

@@ -559,14 +559,21 @@ async def get_library_neighbors(
     if not path:
         return LibraryNeighborsResponse(prev=None, next=None, path=None)
 
-    # 같은 path (정확히) 의 자료들 — title 오름차순
+    # 같은 path (정확히) 의 자료들 — title 오름차순.
+    # user_tags 는 JSONB. 다른 endpoint 와 일관되게 EXISTS + jsonb_array_elements_text 사용.
+    from sqlalchemy import text as sql_text
     exact_tag = f"{LIBRARY_PREFIX}{path}"
     res = await session.execute(
         select(Document.id, Document.title)
         .where(
             Document.deleted_at == None,  # noqa: E711
             Document.category == "library",
-            Document.user_tags.op("@>")(f'["{exact_tag}"]'),
+            sql_text("""
+                EXISTS (
+                    SELECT 1 FROM jsonb_array_elements_text(documents.user_tags) AS t
+                    WHERE t = :exact
+                )
+            """).bindparams(exact=exact_tag),
         )
         .order_by(Document.title.asc().nullslast(), Document.id.asc())
     )