docs(uiux): UIUX 设计方案大改 + 5 份作业指导书对齐 + 开发任务文档

- UIUX 文档：填充 19 个缺口（多主体画像/健康度/AI+看板/增长域/洞察域/创始人端/OODA/助推/商密）
- UIUX 文档：插入 6 个新章节（十四~十九），旧章节重编号为二十~三十一，更新目录和交叉引用
- 作业指导书 x5：导航改为 6 域分组，新增 Context Bar/工作模式/Insight Rail/决策线程/多工作区等 UI 概念
- 新建 docs/2-task-uiux.md：50 个代码落地开发任务，按 P0-P6 分优先级 + 8 Sprint 规划
- 后端/前端：大量新增模型、路由、组件（来自之前 Phase 开发）

backend/app/routers/digital_twins.py

@@ -0,0 +1,47 @@
+"""数字孪生路由。"""
+
+from fastapi import APIRouter, Depends, Query
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.core.database import get_db
+from app.core.dependencies import get_current_user
+from app.models.digital_twin import DigitalTwinModel
+from app.models.user import User
+from app.schemas.common import ApiResponse, success
+from app.services.digital_twin_engine import build_twin_model, simulate_scenario
+
+router = APIRouter(prefix="/digital-twins", tags=["digital-twins"])
+
+
+@router.get("", response_model=ApiResponse[list])
+async def list_twins(company_id: str = Query(...), db: AsyncSession = Depends(get_db), user: User = Depends(get_current_user)):
+    """获取数字孪生模型列表。"""
+    result = await db.execute(
+        select(DigitalTwinModel).where(DigitalTwinModel.company_id == company_id)
+    )
+    items = result.scalars().all()
+    return success(data=[
+        {
+            "id": str(i.id),
+            "company_id": str(i.company_id),
+            "model_params": i.model_params,
+            "scenarios": i.scenarios,
+            "accuracy_score": i.accuracy_score,
+        }
+        for i in items
+    ])
+
+
+@router.post("/build", response_model=ApiResponse[dict])
+async def build_twin(req: dict, user: User = Depends(get_current_user)):
+    """构建数字孪生模型。"""
+    result = await build_twin_model(req.get("company_data", ""))
+    return success(data=result)
+
+
+@router.post("/simulate", response_model=ApiResponse[dict])
+async def simulate(req: dict, user: User = Depends(get_current_user)):
+    """模拟决策场景。"""
+    result = await simulate_scenario(req.get("model_params", {}), req.get("scenario", ""))
+    return success(data=result)