feat: add Skill model

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/models/skill.py

@@ -0,0 +1,22 @@
+from sqlalchemy import Column, String, Text, Boolean, JSON, ForeignKey
+from sqlalchemy.orm import relationship
+from app.models.base import BaseModel
+
+
+class Skill(BaseModel):
+    __tablename__ = "skills"
+
+    name = Column(String(100), nullable=False, unique=True, index=True)
+    description = Column(Text, nullable=True)  # 供 LLM 理解用途
+    instructions = Column(Text, nullable=False)  # Agent 执行时的指令模板
+    agent_type = Column(String(50), nullable=False, index=True)  # master/planner/executor/librarian/analyst
+    tools = Column(JSON, default=list)  # 引用的工具名称列表
+    required_context = Column(JSON, default=list)  # 需要的前置数据
+    output_format = Column(Text, nullable=True)  # 输出格式要求
+    visibility = Column(String(20), default="private")  # private/team/market
+    team_id = Column(String(36), ForeignKey("users.id"), nullable=True)
+    is_active = Column(Boolean, default=True)
+    owner_id = Column(String(36), ForeignKey("users.id"), nullable=False)
+
+    owner = relationship("User", foreign_keys=[owner_id])
+    team = relationship("User", foreign_keys=[team_id])