feat: add demand page modules and admin endpoints

Add full backend support for a demand request page, including:
- New database models for demand hero, feature cards, form configuration, and product recommendations
- Alembic migration for the new tables
- Default seed data for demand page components
- Public site config endpoint exposing demand data
- Admin CRUD operations and configuration for demand modules
- Extended lead query filters for source page, keyword, and date range
- Updated Pydantic schemas for lead query parameters
- Comprehensive test coverage for all new endpoints

app/demand_recommendations.py

@@ -0,0 +1,66 @@
+from fastapi import HTTPException
+from sqlalchemy import delete, select
+from sqlalchemy.orm import Session, selectinload
+
+from .models import DemandRecommendation, DemandRecommendationProduct, Product
+from .serializers import model_dict
+
+
+def demand_recommendation_error(status_code: int, message: str, code: str, details: dict | None = None) -> None:
+    raise HTTPException(status_code=status_code, detail={"message": message, "code": code, "details": details or {}})
+
+
+def demand_recommendation_dict(item: DemandRecommendation, *, public: bool = False) -> dict:
+    links = sorted(item.products or [], key=lambda link: (link.sortOrder, link.productId))
+    if public:
+        links = [link for link in links if link.product and link.product.status == "published"]
+
+    data = {
+        "id": item.id,
+        "title": item.title,
+        "subtitle": item.subtitle,
+        "productIds": [link.productId for link in links],
+        "isActive": item.isActive,
+    }
+    if not public:
+        base = model_dict(item)
+        data.update(
+            {
+                "sortOrder": item.sortOrder,
+                "createdAt": base["createdAt"],
+                "updatedAt": base["updatedAt"],
+            }
+        )
+    return data
+
+
+def demand_recommendation_query():
+    return (
+        select(DemandRecommendation)
+        .options(selectinload(DemandRecommendation.products).selectinload(DemandRecommendationProduct.product))
+        .order_by(DemandRecommendation.sortOrder.asc())
+    )
+
+
+def validate_demand_recommendation_product_ids(db: Session, product_ids: list[str]) -> None:
+    if len(set(product_ids)) != len(product_ids):
+        demand_recommendation_error(422, "推荐线路商品不能重复", "DEMAND_RECOMMENDATION_PRODUCT_DUPLICATE")
+    if not product_ids:
+        return
+
+    products = db.scalars(select(Product).where(Product.id.in_(product_ids))).all()
+    found_ids = {product.id for product in products}
+    missing_ids = [product_id for product_id in product_ids if product_id not in found_ids]
+    if missing_ids:
+        demand_recommendation_error(422, "推荐线路商品不存在", "DEMAND_RECOMMENDATION_PRODUCT_NOT_FOUND", {"productIds": missing_ids})
+
+
+def replace_demand_recommendation_products(db: Session, recommendation: DemandRecommendation, product_ids: list[str]) -> None:
+    validate_demand_recommendation_product_ids(db, product_ids)
+    db.execute(delete(DemandRecommendationProduct).where(DemandRecommendationProduct.recommendationId == recommendation.id))
+    db.flush()
+    recommendation.products = []
+    for index, product_id in enumerate(product_ids):
+        link = DemandRecommendationProduct(recommendationId=recommendation.id, productId=product_id, sortOrder=index)
+        recommendation.products.append(link)
+        db.add(link)