fix: 검색 UX 개선 — Enter 키 기반 + 한국어 검색 ILIKE fallback

- 프론트: debounce 자동검색 제거 → Enter 키로만 검색 (한글 조합 문제 해결)
- 백엔드: trgm threshold 0.1로 낮춤 + ILIKE '%검색어%' fallback 추가
- hybrid 검색 score threshold 0.01 → 0.001로 낮춤

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/api/search.py

@@ -93,17 +93,21 @@ async def _search_fts(session: AsyncSession, query: str, limit: int) -> list[Sea
 
 
 async def _search_trgm(session: AsyncSession, query: str, limit: int) -> list[SearchResult]:
-    """트리그램 부분매칭 (한국어 지원)"""
+    """트리그램 부분매칭 + ILIKE fallback (한국어 지원)"""
+    # threshold 낮춰서 한국어 매칭 향상
+    await session.execute(text("SET pg_trgm.similarity_threshold = 0.1"))
     result = await session.execute(
         text("""
             SELECT id, title, ai_domain, ai_summary, file_format,
-                   similarity(
-                       coalesce(title, '') || ' ' || coalesce(extracted_text, ''),
-                       :query
+                   GREATEST(
+                       similarity(coalesce(title, '') || ' ' || coalesce(extracted_text, ''), :query),
+                       CASE WHEN (coalesce(title, '') || ' ' || coalesce(extracted_text, '')) ILIKE '%' || :query || '%'
+                            THEN 0.5 ELSE 0 END
                    ) AS score,
                    left(extracted_text, 200) AS snippet
             FROM documents
             WHERE (coalesce(title, '') || ' ' || coalesce(extracted_text, '')) %% :query
+               OR (coalesce(title, '') || ' ' || coalesce(extracted_text, '')) ILIKE '%' || :query || '%'
             ORDER BY score DESC
             LIMIT :limit
         """),
@@ -182,8 +186,9 @@ async def _search_hybrid(session: AsyncSession, query: str, limit: int) -> list[
                 FROM documents d
                 {vector_clause}
                 WHERE coalesce(d.extracted_text, '') != ''
+                   OR (coalesce(d.title, '') || ' ' || coalesce(d.extracted_text, '')) ILIKE '%' || :query || '%'
             ) sub
-            WHERE sub.score > 0.01
+            WHERE sub.score > 0.001
             ORDER BY sub.score DESC
             LIMIT :limit
         """),