Enhance agent workflows and tools: unify subscription and download processes, add site querying functionality, and improve error handling in download operations.

app/db/models/site.py

@@ -66,6 +66,12 @@ class Site(Base):
         result = await db.execute(select(cls).where(cls.domain == domain))
         return result.scalar_one_or_none()
 
+    @classmethod
+    @async_db_query
+    async def async_get_by_name(cls, db: AsyncSession, name: str):
+        result = await db.execute(select(cls).where(cls.name == name))
+        return result.scalar_one_or_none()
+
     @classmethod
     @db_query
     def get_actives(cls, db: Session):