feat: persist system settings and refine admin layouts

backend/app/models/__init__.py

@@ -2,14 +2,18 @@ from app.models.user import User
 from app.models.gpu_cluster import GPUCluster
 from app.models.task import CollectionTask
 from app.models.datasource import DataSource
+from app.models.datasource_config import DataSourceConfig
 from app.models.alert import Alert, AlertSeverity, AlertStatus
+from app.models.system_setting import SystemSetting
 
 __all__ = [
     "User",
     "GPUCluster",
     "CollectionTask",
     "DataSource",
+    "DataSourceConfig",
+    "SystemSetting",
     "Alert",
     "AlertSeverity",
     "AlertStatus",
-]
+]

backend/app/models/system_setting.py

@@ -0,0 +1,19 @@
+"""Persistent system settings model."""
+
+from sqlalchemy import JSON, Column, DateTime, Integer, String, UniqueConstraint
+from sqlalchemy.sql import func
+
+from app.db.session import Base
+
+
+class SystemSetting(Base):
+    __tablename__ = "system_settings"
+    __table_args__ = (UniqueConstraint("category", name="uq_system_settings_category"),)
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    category = Column(String(50), nullable=False)
+    payload = Column(JSON, nullable=False, default={})
+    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now())
+
+    def __repr__(self):
+        return f"<SystemSetting {self.category}>"