feat: 完成布局优化 - 操作列固定、批量按钮自适应、分类标签带数量

优化内容:
1. 表格布局:
   - 使用 calc(100vw - 160px) 确保表格不超出视口
   - 操作列 fixed='right' 固定在右侧，宽度 300px
   - 按钮 3 个后自动换行 (max-width: 200px)
   - 恢复合理列宽，不再过度压缩

2. 批量操作区域:
   - 容器改为 inline-block，宽度自适应按钮内容
   - 背景宽度与按钮总宽度匹配

3. 分类标签:
   - 显示数量 (如 '待处理 (20)')
   - 点击切换筛选，去掉误导的 'X' 图标

4. 删除功能:
   - 操作列增加删除按钮
   - 删除前弹出确认对话框

5. 系统日志:
   - 修复后端日志路径 (parents[4])
   - 404 时显示友好提示

6. 其他:
   - 左侧菜单宽度 160px
   - 所有功能保留 (登录、用户管理、批量操作等)

platform/backend/models/__init__.py

@@ -0,0 +1,77 @@
+# 宇之然内容创作平台 - 数据模型
+
+from sqlalchemy import Column, Integer, String, DateTime, JSON, Boolean, func, Float
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.dialects.postgresql import UUID
+import uuid
+
+Base = declarative_base()
+
+class User(Base):
+    __tablename__ = "users"
+
+    id = Column(Integer, primary_key=True, index=True)
+    username = Column(String(50), unique=True, index=True, nullable=False)
+    password_hash = Column(String(100), nullable=False)
+    role = Column(String(20), default="user")  # user | admin
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    last_login = Column(DateTime(timezone=True))
+
+class Topic(Base):
+    __tablename__ = "topics"
+
+    id = Column(Integer, primary_key=True, index=True)
+    title = Column(String(500), nullable=False)
+    field = Column(String(100))
+    priority_score = Column(Integer, default=0)
+    status = Column(String(50), default="待处理")  # 待处理 | 待审查 | 待发布 | 已发布
+    compliance_score = Column(Float, default=0.0)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(
+        DateTime(timezone=True),
+        server_default=func.now(),
+        onupdate=func.now()
+    )
+    generated_at = Column(DateTime(timezone=True))  # 新增字段
+    published_at = Column(DateTime(timezone=True))   # 新增字段
+    published_urls = Column(JSON)                    # {"zhihu": "url", ...}
+
+class AuditLog(Base):
+    __tablename__ = "audit_logs"
+
+    id = Column(Integer, primary_key=True, index=True)
+    user_id = Column(Integer, index=True)
+    action = Column(String(50), index=True)         # login, create_user, delete_user, publish
+    resource_type = Column(String(50))              # user, topic, article
+    resource_id = Column(Integer)
+    details = Column(String(500))
+    ip_address = Column(String(45))
+    user_agent = Column(String(200))
+    timestamp = Column(DateTime(timezone=True), server_default=func.now())
+
+class GenerateTask(Base):
+    __tablename__ = "generate_tasks"
+
+    id = Column(Integer, primary_key=True, index=True)
+    topic_id = Column(Integer, index=True)
+    status = Column(String(20), default="pending")  # pending, processing, completed, failed
+    result = Column(JSON)                           # 存储生成结果或错误信息
+    created_by = Column(Integer)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(
+        DateTime(timezone=True),
+        server_default=func.now(),
+        onupdate=func.now()
+    )
+
+class PublishRecord(Base):
+    __tablename__ = "publish_records"
+
+    id = Column(Integer, primary_key=True, index=True)
+    topic_id = Column(Integer, index=True)
+    platform = Column(String(50))                   # zhihu, wechat, xiaohongshu
+    url = Column(String(500))
+    status = Column(String(20), default="success")  # success, failed
+    error_message = Column(String(500))
+    created_by = Column(Integer)
+    created_at = Column(DateTime(timezone=True), server_default=func.now())