Add FastAPI backend with agent system

backend/app/schemas/task.py

@@ -0,0 +1,39 @@
+from pydantic import BaseModel
+from datetime import datetime
+from app.models.task import TaskStatus, TaskPriority
+
+
+class TaskCreate(BaseModel):
+    title: str
+    description: str | None = None
+    priority: TaskPriority = TaskPriority.MEDIUM
+    due_date: datetime | None = None
+    tags: list[str] | None = None
+
+
+class TaskUpdate(BaseModel):
+    title: str | None = None
+    description: str | None = None
+    status: TaskStatus | None = None
+    priority: TaskPriority | None = None
+    due_date: datetime | None = None
+    tags: list[str] | None = None
+
+
+class TaskOut(BaseModel):
+    id: str
+    title: str
+    description: str | None
+    status: TaskStatus
+    priority: TaskPriority
+    due_date: datetime | None
+    completed_at: datetime | None
+    tags: str | None
+    created_at: datetime
+    updated_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class DailyPlanRequest(BaseModel):
+    user_id: str