fix(agents): AgentRepository 空串 port 不再被拦截，修复服务端查不到/删不掉智能体

require_port 单角色后恒定 port=''，但 AgentRepository 用 if not port 把空串当无 port 直接返回空/None，导致 GET /agents 永远为空、GET/DELETE 404 'Agent not found'；本地删除依赖服务端先删身份，被 404 卡死后本地也无法删除。改为 if port is None 后空串正常参与查询。

app/infrastructure/repositories.py

@@ -1065,21 +1065,21 @@ class AgentRepository:
         }
 
     async def get_by_user(self, user_id: str, port: str | None = None) -> list[dict]:
-        if not port:
+        if port is None:
             return []
         stmt = select(Agent).where(Agent.user_id == user_id, Agent.port == port)
         rows = await self.session.scalars(stmt.order_by(Agent.created_at))
         return [self._to_dict(a) for a in rows]
 
     async def get(self, agent_id: str, user_id: str, port: str | None = None) -> dict | None:
-        if not port:
+        if port is None:
             return None
         stmt = select(Agent).where(Agent.id == agent_id, Agent.user_id == user_id, Agent.port == port)
         a = await self.session.scalar(stmt)
         return self._to_dict(a) if a else None
 
     async def count_by_user(self, user_id: str, port: str | None = None) -> int:
-        if not port:
+        if port is None:
             return 0
         stmt = select(Agent.id).where(Agent.user_id == user_id, Agent.port == port)
         return len(list(await self.session.scalars(stmt)))
@@ -1114,7 +1114,7 @@ class AgentRepository:
         return self._to_dict(a)
 
     async def update(self, agent_id: str, user_id: str, fields: dict, port: str | None = None) -> dict | None:
-        if not port:
+        if port is None:
             return None
         stmt = select(Agent).where(Agent.id == agent_id, Agent.user_id == user_id, Agent.port == port)
         a = await self.session.scalar(stmt)
@@ -1134,7 +1134,7 @@ class AgentRepository:
         return self._to_dict(a)
 
     async def delete(self, agent_id: str, user_id: str, port: str | None = None) -> bool:
-        if not port:
+        if port is None:
             return False
         stmt = select(Agent).where(Agent.id == agent_id, Agent.user_id == user_id, Agent.port == port)
         a = await self.session.scalar(stmt)