feat: 注册知识入库接口 + 优化大规模知识图谱力导向布局

- 后端 Gateway 挂载 /api/knowledge-ingest 路由（发布 md 制品）
- 知识图谱力模拟按节点规模缩放斥力/截断距离/冷却速率，避免数百节点时布局长时间不收敛
- 斥力与碰撞改为基于均匀网格的近邻对计算，并增加每帧最大位移限制防止抖动与飞出

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

offline-backend-20260512/backend/app/gateway/app.py

@@ -40,6 +40,7 @@ from app.gateway.routers import (
     html_page_favorites,
     intent,
     knowledge,
+    knowledge_ingest,
     light_apps,
     llm_metrics,
     mcp,
@@ -1359,6 +1360,9 @@ This gateway provides custom endpoints for models, MCP configuration, skills, an
     # Product knowledge base API is mounted at /api/knowledge
     app.include_router(knowledge.router)
 
+    # External knowledge ingest (publish md artifacts) at /api/knowledge-ingest
+    app.include_router(knowledge_ingest.router)
+
     # System settings API is mounted at /api/system-settings
     app.include_router(system_settings.router)