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/models.py

@@ -207,6 +207,7 @@ class Product(Base):
     images: Mapped[list["ProductImage"]] = relationship(back_populates="product", cascade="all, delete-orphan")
     campaignLinks: Mapped[list["CampaignProduct"]] = relationship(back_populates="product", cascade="all, delete-orphan")
     routeSectionLinks: Mapped[list["RouteSectionProduct"]] = relationship(back_populates="product", cascade="all, delete-orphan")
+    demandRecommendationLinks: Mapped[list["DemandRecommendationProduct"]] = relationship(back_populates="product", cascade="all, delete-orphan")
     leads: Mapped[list["Lead"]] = relationship(back_populates="sourceProduct")
     orders: Mapped[list["Order"]] = relationship(back_populates="product")
 
@@ -279,6 +280,74 @@ class RouteSectionProduct(Base):
     product: Mapped[Product] = relationship(back_populates="routeSectionLinks")
 
 
+class DemandHero(Base):
+    __tablename__ = "DemandHero"
+
+    id: Mapped[str] = mapped_column(String, primary_key=True, default=new_id)
+    title: Mapped[str] = mapped_column(String, nullable=False)
+    kicker: Mapped[str | None] = mapped_column(String)
+    description: Mapped[str | None] = mapped_column(Text)
+    steps: Mapped[list[str]] = mapped_column(ARRAY(String), default=list, nullable=False)
+    sortOrder: Mapped[int] = mapped_column(Integer, default=0, nullable=False)
+    isActive: Mapped[bool] = mapped_column(Boolean, default=True, nullable=False)
+    createdAt: Mapped[datetime] = mapped_column(DateTime, default=utc_now, nullable=False)
+    updatedAt: Mapped[datetime] = mapped_column(DateTime, default=utc_now, onupdate=utc_now, nullable=False)
+
+
+class DemandFeatureCard(Base):
+    __tablename__ = "DemandFeatureCard"
+
+    id: Mapped[str] = mapped_column(String, primary_key=True, default=new_id)
+    title: Mapped[str] = mapped_column(String, nullable=False)
+    description: Mapped[str | None] = mapped_column(Text)
+    sortOrder: Mapped[int] = mapped_column(Integer, default=0, nullable=False)
+    isActive: Mapped[bool] = mapped_column(Boolean, default=True, nullable=False)
+    createdAt: Mapped[datetime] = mapped_column(DateTime, default=utc_now, nullable=False)
+    updatedAt: Mapped[datetime] = mapped_column(DateTime, default=utc_now, onupdate=utc_now, nullable=False)
+
+
+class DemandForm(Base):
+    __tablename__ = "DemandForm"
+
+    id: Mapped[str] = mapped_column(String, primary_key=True, default=new_id)
+    destinationLabel: Mapped[str] = mapped_column(String, default="目的地/玩法", nullable=False)
+    destinationPlaceholder: Mapped[str | None] = mapped_column(String)
+    phoneLabel: Mapped[str] = mapped_column(String, default="联系方式", nullable=False)
+    phonePlaceholder: Mapped[str | None] = mapped_column(String)
+    noteLabel: Mapped[str] = mapped_column(String, default="补充说明", nullable=False)
+    notePlaceholder: Mapped[str | None] = mapped_column(String)
+    submitLabel: Mapped[str] = mapped_column(String, default="提交出行需求", nullable=False)
+    chips: Mapped[list[str]] = mapped_column(ARRAY(String), default=list, nullable=False)
+    isActive: Mapped[bool] = mapped_column(Boolean, default=True, nullable=False)
+    createdAt: Mapped[datetime] = mapped_column(DateTime, default=utc_now, nullable=False)
+    updatedAt: Mapped[datetime] = mapped_column(DateTime, default=utc_now, onupdate=utc_now, nullable=False)
+
+
+class DemandRecommendation(Base):
+    __tablename__ = "DemandRecommendation"
+
+    id: Mapped[str] = mapped_column(String, primary_key=True, default=new_id)
+    title: Mapped[str] = mapped_column(String, nullable=False)
+    subtitle: Mapped[str | None] = mapped_column(Text)
+    sortOrder: Mapped[int] = mapped_column(Integer, default=0, nullable=False)
+    isActive: Mapped[bool] = mapped_column(Boolean, default=True, nullable=False)
+    createdAt: Mapped[datetime] = mapped_column(DateTime, default=utc_now, nullable=False)
+    updatedAt: Mapped[datetime] = mapped_column(DateTime, default=utc_now, onupdate=utc_now, nullable=False)
+
+    products: Mapped[list["DemandRecommendationProduct"]] = relationship(back_populates="recommendation", cascade="all, delete-orphan")
+
+
+class DemandRecommendationProduct(Base):
+    __tablename__ = "DemandRecommendationProduct"
+
+    recommendationId: Mapped[str] = mapped_column(String, ForeignKey("DemandRecommendation.id", ondelete="CASCADE"), primary_key=True)
+    productId: Mapped[str] = mapped_column(String, ForeignKey("Product.id", ondelete="CASCADE"), primary_key=True)
+    sortOrder: Mapped[int] = mapped_column(Integer, default=0, nullable=False)
+
+    recommendation: Mapped[DemandRecommendation] = relationship(back_populates="products")
+    product: Mapped[Product] = relationship(back_populates="demandRecommendationLinks")
+
+
 class Lead(Base):
     __tablename__ = "Lead"