feat: 凭证生成、成本分析、AI问答、前端页面、集成测试与E2E测试

- 后端: 凭证生成引擎、金蝶导出器、凭证模板服务
- 后端: 成本分析服务、AI问答服务
- 后端: 科目映射CRUD API、分析API、QA API
- 后端: 集成测试(认证/任务/凭证) 49个测试全部通过
- 前端: 凭证管理、成本分析、导出中心、知识库、系统设置页面
- 前端: AuthGuard认证守卫、Dashboard AI聊天功能
- 前端: Playwright E2E测试 16 passed, 1 skipped
- 基础设施: Docker Compose、Nginx反向代理、.env.example
- 文档: 用户手册、管理员手册、发布检查清单

backend/app/api/qa.py

@@ -0,0 +1,68 @@
+"""
+问答 API
+
+提供预置问题列表和问题回答接口
+"""
+
+from typing import List
+
+from fastapi import APIRouter, Depends, HTTPException, Body
+from pydantic import BaseModel
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.core.database import get_db
+from app.core.tenant import get_current_company_id
+from app.services.ai.qa_service import QAService
+
+router = APIRouter(prefix="/api/qa", tags=["问答"])
+
+
+class QuestionRequest(BaseModel):
+    """问题请求"""
+    task_id: int
+    question: str
+    context: str = ""
+
+
+class QuestionResponse(BaseModel):
+    """问题响应"""
+    answer: str
+    data_points: List[str] = []
+
+
+class SuggestedQuestionsResponse(BaseModel):
+    """建议问题响应"""
+    questions: List[str]
+
+
+@router.get("/suggested-questions", response_model=SuggestedQuestionsResponse)
+async def get_suggested_questions(
+    task_id: int,
+    context: str = "",
+    db: AsyncSession = Depends(get_db),
+    company_id: int = Depends(get_current_company_id),
+) -> SuggestedQuestionsResponse:
+    """
+    获取预置问题列表
+
+    根据任务状态返回合适的预置问题
+    """
+    service = QAService(db)
+    questions = await service.get_suggested_questions(task_id, context)
+    return SuggestedQuestionsResponse(questions=questions)
+
+
+@router.post("/ask", response_model=QuestionResponse)
+async def ask_question(
+    request: QuestionRequest,
+    db: AsyncSession = Depends(get_db),
+    company_id: int = Depends(get_current_company_id),
+) -> QuestionResponse:
+    """
+    回答用户问题
+
+    基于真实数据回答预置问题
+    """
+    service = QAService(db)
+    answer = await service.answer_preset_question(request.task_id, request.question)
+    return QuestionResponse(answer=answer, data_points=[])