新增点赞收藏功能：cloud_favorites 模型、查询/设置点赞状态及收藏列表接口

app/models.py

@@ -236,3 +236,33 @@ class UserCollection(Base):
 
     cloud_type: Mapped[CloudType] = relationship(lazy="raise")
     first_cloud: Mapped[Cloud | None] = relationship(lazy="raise")
+
+
+class CloudFavorite(Base):
+    """用户对照片的点赞/收藏记录。"""
+
+    __tablename__ = "cloud_favorites"
+    __table_args__ = (
+        UniqueConstraint("user_id", "cloud_id", name="uq_cloud_favorites_user_cloud"),
+        Index("ix_cloud_favorites_user_id", "user_id"),
+        Index("ix_cloud_favorites_cloud_id", "cloud_id"),
+        Index(
+            "ix_cloud_favorites_user_created",
+            "user_id",
+            text("created_at DESC"),
+            text("id DESC"),
+        ),
+    )
+
+    id: Mapped[uuid.UUID] = mapped_column(Uuid, primary_key=True, default=uuid.uuid4)
+    user_id: Mapped[uuid.UUID] = mapped_column(
+        Uuid, ForeignKey("users.id", ondelete="CASCADE"), nullable=False
+    )
+    cloud_id: Mapped[uuid.UUID] = mapped_column(
+        Uuid, ForeignKey("clouds.id", ondelete="CASCADE"), nullable=False
+    )
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), nullable=False
+    )
+
+    cloud: Mapped[Cloud] = relationship(lazy="raise")