🎉 Initial commit: QQuiz - 智能刷题与题库管理平台

## 功能特性

✅ **核心功能**
- 多文件上传与智能去重（基于 content_hash）
- 异步文档解析（支持 TXT/PDF/DOCX/XLSX）
- AI 智能题目提取与评分（OpenAI/Anthropic/Qwen）
- 断点续做与进度管理
- 自动错题本收集

✅ **技术栈**
- Backend: FastAPI + SQLAlchemy 2.0 + PostgreSQL
- Frontend: React 18 + Vite + Tailwind CSS
- Deployment: Docker Compose

✅ **项目结构**
- 53 个文件
- 完整的前后端分离架构
- Docker/源码双模部署支持

🚀 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/models.py

@@ -0,0 +1,134 @@
+"""
+SQLAlchemy Models for QQuiz Platform
+"""
+from datetime import datetime
+from enum import Enum as PyEnum
+from sqlalchemy import (
+    Column, Integer, String, Boolean, DateTime,
+    ForeignKey, Text, JSON, Index, Enum
+)
+from sqlalchemy.orm import relationship, declarative_base
+from sqlalchemy.sql import func
+
+Base = declarative_base()
+
+
+class ExamStatus(str, PyEnum):
+    """Exam processing status"""
+    PENDING = "pending"
+    PROCESSING = "processing"
+    READY = "ready"
+    FAILED = "failed"
+
+
+class QuestionType(str, PyEnum):
+    """Question types"""
+    SINGLE = "single"      # 单选
+    MULTIPLE = "multiple"  # 多选
+    JUDGE = "judge"        # 判断
+    SHORT = "short"        # 简答
+
+
+class User(Base):
+    """User model"""
+    __tablename__ = "users"
+
+    id = Column(Integer, primary_key=True, index=True)
+    username = Column(String(50), unique=True, nullable=False, index=True)
+    hashed_password = Column(String(255), nullable=False)
+    is_admin = Column(Boolean, default=False, nullable=False)
+    created_at = Column(DateTime(timezone=True), server_default=func.now(), nullable=False)
+
+    # Relationships
+    exams = relationship("Exam", back_populates="user", cascade="all, delete-orphan")
+    mistakes = relationship("UserMistake", back_populates="user", cascade="all, delete-orphan")
+
+    def __repr__(self):
+        return f"<User(id={self.id}, username='{self.username}', is_admin={self.is_admin})>"
+
+
+class SystemConfig(Base):
+    """System configuration key-value store"""
+    __tablename__ = "system_configs"
+
+    key = Column(String(100), primary_key=True)
+    value = Column(Text, nullable=False)
+    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now())
+
+    def __repr__(self):
+        return f"<SystemConfig(key='{self.key}', value='{self.value}')>"
+
+
+class Exam(Base):
+    """Exam (Question Bank Container)"""
+    __tablename__ = "exams"
+
+    id = Column(Integer, primary_key=True, index=True)
+    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False)
+    title = Column(String(200), nullable=False)
+    status = Column(Enum(ExamStatus), default=ExamStatus.PENDING, nullable=False, index=True)
+    current_index = Column(Integer, default=0, nullable=False)
+    total_questions = Column(Integer, default=0, nullable=False)
+    created_at = Column(DateTime(timezone=True), server_default=func.now(), nullable=False)
+    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now())
+
+    # Relationships
+    user = relationship("User", back_populates="exams")
+    questions = relationship("Question", back_populates="exam", cascade="all, delete-orphan")
+
+    # Indexes
+    __table_args__ = (
+        Index('ix_exams_user_status', 'user_id', 'status'),
+    )
+
+    def __repr__(self):
+        return f"<Exam(id={self.id}, title='{self.title}', status={self.status}, questions={self.total_questions})>"
+
+
+class Question(Base):
+    """Question model"""
+    __tablename__ = "questions"
+
+    id = Column(Integer, primary_key=True, index=True)
+    exam_id = Column(Integer, ForeignKey("exams.id", ondelete="CASCADE"), nullable=False)
+    content = Column(Text, nullable=False)
+    type = Column(Enum(QuestionType), nullable=False)
+    options = Column(JSON, nullable=True)  # For single/multiple choice: ["A. Option1", "B. Option2", ...]
+    answer = Column(Text, nullable=False)
+    analysis = Column(Text, nullable=True)
+    content_hash = Column(String(32), nullable=False, index=True)  # MD5 hash for deduplication
+    created_at = Column(DateTime(timezone=True), server_default=func.now(), nullable=False)
+
+    # Relationships
+    exam = relationship("Exam", back_populates="questions")
+    mistakes = relationship("UserMistake", back_populates="question", cascade="all, delete-orphan")
+
+    # Indexes for deduplication within exam scope
+    __table_args__ = (
+        Index('ix_questions_exam_hash', 'exam_id', 'content_hash'),
+    )
+
+    def __repr__(self):
+        return f"<Question(id={self.id}, type={self.type}, hash={self.content_hash[:8]}...)>"
+
+
+class UserMistake(Base):
+    """User mistake records (错题本)"""
+    __tablename__ = "user_mistakes"
+
+    id = Column(Integer, primary_key=True, index=True)
+    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False)
+    question_id = Column(Integer, ForeignKey("questions.id", ondelete="CASCADE"), nullable=False)
+    created_at = Column(DateTime(timezone=True), server_default=func.now(), nullable=False)
+
+    # Relationships
+    user = relationship("User", back_populates="mistakes")
+    question = relationship("Question", back_populates="mistakes")
+
+    # Unique constraint to prevent duplicates
+    __table_args__ = (
+        Index('ix_user_mistakes_unique', 'user_id', 'question_id', unique=True),
+    )
+
+    def __repr__(self):
+        return f"<UserMistake(user_id={self.user_id}, question_id={self.question_id})>"