初始提交：项目基础结构

- backend: FastAPI 后端服务 (Python)
- frontend: React + Tauri 前端应用
- docker-compose.yml: 容器编排配置

backend/app/models/task.py

@@ -0,0 +1,59 @@
+"""任务模型 — 支持无限嵌套"""
+import uuid
+from datetime import datetime, timezone
+from sqlalchemy import String, DateTime, Boolean, ForeignKey
+from sqlalchemy.dialects.postgresql import UUID
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.models.base import Base
+
+
+class Task(Base):
+    __tablename__ = "tasks"
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), primary_key=True, default=uuid.uuid4,
+    )
+
+    # ---- 物理外键（关联本库 products） ----
+    product_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("products.id"), nullable=False, comment="所属产品ID",
+    )
+
+    # ---- 物理外键（自引用：无限嵌套父子任务） ----
+    parent_task_id: Mapped[uuid.UUID | None] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("tasks.id"), nullable=True, index=True, comment="父任务ID",
+    )
+
+    task_name: Mapped[str] = mapped_column(
+        String(200), nullable=False, comment="任务名称",
+    )
+
+    # ---- 逻辑外键（关联老系统用户表，仅存储 ID，无物理约束） ----
+    assignee_id: Mapped[str | None] = mapped_column(
+        String(64), nullable=True, comment="负责人ID(逻辑外键→老系统)",
+    )
+
+    status: Mapped[str] = mapped_column(
+        String(50), nullable=False, default="pending", comment="任务状态",
+    )
+
+    notify_parent_on_complete: Mapped[bool] = mapped_column(
+        Boolean, default=False, comment="完成后是否通知父任务",
+    )
+
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), default=lambda: datetime.now(timezone.utc), comment="创建时间",
+    )
+
+    # ---- 关系 ----
+    product: Mapped["Product"] = relationship("Product", lazy="selectin")
+    parent_task: Mapped["Task | None"] = relationship(
+        "Task", remote_side="Task.id", back_populates="child_tasks", lazy="selectin",
+    )
+    child_tasks: Mapped[list["Task"]] = relationship(
+        "Task", back_populates="parent_task", lazy="selectin",
+    )
+
+    def __repr__(self) -> str:
+        return f"<Task {self.task_name}>"