feat(bulk): reorganize context menu with sections and submenu for workflow actions

Group 15 flat menu items into 5 logical sections (Workflow, Metadata,
Attributes, Organize, Download) with section headers to reduce cognitive
load. Nest the three workflow-related actions (Append, Replace, Copy
Syntax) into a single "Send to Workflow" hover-triggered submenu.

Add submenu infrastructure to BaseContextMenu with mouseover/mouseout
boundary detection, 250ms close delay, and viewport-aware positioning.

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

locales/ko.json

@@ -696,6 +696,14 @@
             "clear": "선택 지우기",
             "skipMetadataRefreshCount": "건너뛰기（{count}개 모델）",
             "resumeMetadataRefreshCount": "재개（{count}개 모델）",
+            "sendToWorkflow": "워크플로우로 보내기",
+            "sections": {
+                "workflow": "워크플로우",
+                "metadata": "메타데이터",
+                "attributes": "속성",
+                "organize": "정리",
+                "download": "다운로드"
+            },
             "autoOrganizeProgress": {
                 "initializing": "자동 정리 초기화 중...",
                 "starting": "{type}에 대한 자동 정리 시작...",