fix(market): 补齐MarketApp ORM category/tags字段 + 硬化导入管道(空内容兜底生成SKILL.md + GitHub直链归一)

backend/python/app/models.py

@@ -286,6 +286,10 @@ class MarketApp(Base):
     publisher_id = Column(String(36), ForeignKey("users.id"), default=None)
     publisher_name = Column(String(100), default=None)
     description = Column(Text, default=None)
+    # 分类与标签：DB 表 market_apps 已存在 category(varchar50)/tags(varchar500) 两列，
+    # 此前 ORM 漏声明导致后台读取分类恒为 None -> 回退 "other"（#679 根因）。此处补齐。
+    category = Column(String(50), default="other", comment="技能/应用分类(9类: writing/coding/data_analysis/qa/automation/creativity/communication/reasoning/other)")
+    tags = Column(String(500), default=None, comment="标签,逗号分隔")
     icon = Column(String(500), default=None)
     tutorial = Column(Text, default=None)
     price = Column(DECIMAL(10, 2), nullable=False, default=0.00)