feat: SAC 0.7.4 sidebar system stats block with UI toggle

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/models/__init__.py

@@ -6,6 +6,7 @@ from app.models.notification_cooldown import NotificationCooldown
 from app.models.notification_policy import NotificationPolicy
 from app.models.problem import Problem, ProblemEvent
 from app.models.login_attempt import LoginAttempt
+from app.models.ui_settings import UiSettings
 from app.models.event_severity_override import EventSeverityOverride
 from app.models.user import User
 
@@ -21,4 +22,5 @@ __all__ = [
     "User",
     "EventSeverityOverride",
     "LoginAttempt",
+    "UiSettings",
 ]

backend/app/models/ui_settings.py

@@ -0,0 +1,15 @@
+from sqlalchemy import Boolean
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.database import Base
+
+UI_SETTINGS_ROW_ID = 1
+
+
+class UiSettings(Base):
+    """Singleton: глобальные настройки интерфейса SAC."""
+
+    __tablename__ = "ui_settings"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    show_sidebar_system_stats: Mapped[bool] = mapped_column(Boolean, default=True, nullable=False)