feat: 实现城市手册项目需求 - 数据库模型

- 扩展 User 模型，添加角色和状态字段
- 创建 Region 模型（省市县乡村层级结构）
- 创建版主管理相关模型（申请、权限、支持、限制）
- 创建 Article 模型（文章 + 审核流程）
- 创建 FeaturedService 模型（特色服务 + 审核流程）
- 创建交互功能模型（评论、评分、点赞、收藏）
- 更新 Django settings 注册所有 apps
- 创建需求实施文档

完整实现需求文档中的 12 个核心数据表和审核流程

backend/apps/articles/__init__.py

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+# Articles app

backend/apps/articles/apps.py

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+from django.apps import AppConfig
+
+
+class ArticlesConfig(AppConfig):
+    default_auto_field = 'django.db.models.BigAutoField'
+    name = 'apps.articles'
+    verbose_name = '文章管理'

backend/apps/articles/models.py

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+from django.db import models
+from django.conf import settings
+from apps.regions.models import Region
+
+
+class Article(models.Model):
+    """Model for articles."""
+
+    ARTICLE_TYPE_CHOICES = [
+        ('basic', '城市信息'),
+        ('history', '历史'),
+        ('culture', '文化'),
+        ('practical', '实用'),
+        ('life', '生活'),
+    ]
+
+    STATUS_CHOICES = [
+        ('draft', '草稿'),
+        ('pending_moderator', '待版主审核'),
+        ('pending_ai', '待AI审核'),
+        ('published', '已发布'),
+        ('rejected', '已拒绝'),
+    ]
+
+    MODERATOR_STATUS_CHOICES = [
+        ('pending', '待审核'),
+        ('approved', '通过'),
+        ('rejected', '拒绝'),
+    ]
+
+    AI_STATUS_CHOICES = [
+        ('pending', '待审核'),
+        ('approved', '通过'),
+        ('rejected', '拒绝'),
+    ]
+
+    title = models.CharField(max_length=200, verbose_name='标题')
+    content = models.TextField(verbose_name='内容')
+    region = models.ForeignKey(
+        Region,
+        on_delete=models.CASCADE,
+        related_name='articles',
+        verbose_name='所属版块'
+    )
+    article_type = models.CharField(
+        max_length=20,
+        choices=ARTICLE_TYPE_CHOICES,
+        verbose_name='内容类型'
+    )
+    author = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        on_delete=models.CASCADE,
+        related_name='articles',
+        verbose_name='提交者'
+    )
+
+    # Moderator review
+    moderator_reviewer = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        on_delete=models.SET_NULL,
+        null=True,
+        blank=True,
+        related_name='moderated_articles',
+        verbose_name='版主审核人'
+    )
+    moderator_status = models.CharField(
+        max_length=20,
+        choices=MODERATOR_STATUS_CHOICES,
+        default='pending',
+        verbose_name='版主审核状态'
+    )
+    moderator_reviewed_at = models.DateTimeField(null=True, blank=True, verbose_name='版主审核时间')
+    moderator_rejection_reason = models.TextField(null=True, blank=True, verbose_name='版主拒绝原因')
+
+    # AI review
+    ai_status = models.CharField(
+        max_length=20,
+        choices=AI_STATUS_CHOICES,
+        default='pending',
+        verbose_name='AI审核状态'
+    )
+    ai_reviewed_at = models.DateTimeField(null=True, blank=True, verbose_name='AI审核时间')
+    ai_rejection_reason = models.TextField(null=True, blank=True, verbose_name='AI拒绝原因')
+
+    # Publish status
+    publish_status = models.CharField(
+        max_length=20,
+        choices=STATUS_CHOICES,
+        default='draft',
+        verbose_name='发布状态'
+    )
+    published_at = models.DateTimeField(null=True, blank=True, verbose_name='发布时间')
+
+    created_at = models.DateTimeField(auto_now_add=True, verbose_name='创建时间')
+    updated_at = models.DateTimeField(auto_now=True, verbose_name='更新时间')
+
+    class Meta:
+        db_table = 'articles'
+        verbose_name = '文章'
+        verbose_name_plural = '文章'
+        ordering = ['-created_at']
+
+    def __str__(self):
+        return self.title
+
+    def submit_for_review(self):
+        """Submit article for moderator review."""
+        self.publish_status = 'pending_moderator'
+        self.save()
+
+    def approve_moderator(self, reviewer, reason=''):
+        """Approve article by moderator."""
+        self.moderator_status = 'approved'
+        self.moderator_reviewer = reviewer
+        self.moderator_reviewed_at = timezone.now()
+        self.moderator_rejection_reason = reason
+        self.publish_status = 'pending_ai'
+        self.save()
+
+    def reject_moderator(self, reviewer, reason):
+        """Reject article by moderator."""
+        self.moderator_status = 'rejected'
+        self.moderator_reviewer = reviewer
+        self.moderator_reviewed_at = timezone.now()
+        self.moderator_rejection_reason = reason
+        self.publish_status = 'rejected'
+        self.save()
+
+    def approve_ai(self, reason=''):
+        """Approve article by AI."""
+        self.ai_status = 'approved'
+        self.ai_reviewed_at = timezone.now()
+        self.ai_rejection_reason = reason
+        self.publish_status = 'published'
+        self.published_at = timezone.now()
+        self.save()
+
+    def reject_ai(self, reason):
+        """Reject article by AI."""
+        self.ai_status = 'rejected'
+        self.ai_reviewed_at = timezone.now()
+        self.ai_rejection_reason = reason
+        self.publish_status = 'rejected'
+        self.save()