feat(backend): 添加 API Schemas 定义

- 添加 Chunk 数据结构 (chunk.py)
- 添加 Dataset Schema (dataset.py)
- 添加 Evaluation Schema (eval.py)
- 添加 File Schema (file.py)
- 添加 Project Schema (project.py)
- 添加 Question Schema (question.py)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/schemas/eval.py

@@ -0,0 +1,60 @@
+"""
+Evaluation Dataset Schemas
+"""
+from datetime import datetime
+from typing import Optional, Any
+from uuid import UUID
+from pydantic import BaseModel, ConfigDict, Field
+
+
+class EvalDatasetBase(BaseModel):
+    """Base eval dataset schema"""
+    name: str = Field(..., min_length=1, max_length=255)
+    question_type: Optional[str] = Field("mixed", max_length=50)
+    extra_data: Optional[dict] = None
+
+
+class EvalDatasetCreate(EvalDatasetBase):
+    """Eval dataset create schema"""
+    pass
+
+
+class EvalDatasetUpdate(BaseModel):
+    """Eval dataset update schema"""
+    name: Optional[str] = Field(None, min_length=1, max_length=255)
+    question_type: Optional[str] = Field(None, max_length=50)
+    extra_data: Optional[dict] = None
+
+
+class EvalDatasetResponse(EvalDatasetBase):
+    """Eval dataset response schema"""
+    model_config = ConfigDict(from_attributes=True)
+
+    id: UUID
+    project_id: UUID
+    created_at: datetime
+    updated_at: datetime
+
+
+class TaskBase(BaseModel):
+    """Base task schema"""
+    task_type: str = Field(..., max_length=50)
+    status: Optional[str] = "pending"
+    progress: Optional[int] = Field(0, ge=0, le=100)
+    result: Optional[Any] = None
+    error: Optional[str] = None
+
+
+class TaskResponse(TaskBase):
+    """Task response schema"""
+    model_config = ConfigDict(from_attributes=True)
+
+    id: UUID
+    project_id: Optional[UUID]
+    created_at: datetime
+    updated_at: datetime
+
+
+# Alias for CRUD
+EvalDatasetCreateSchema = EvalDatasetCreate
+EvalDatasetUpdateSchema = EvalDatasetUpdate