Backend overhaul: new models, routers, schemas for shifts, business day, flags, messages, settings

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

local_backend/schemas/settings.py

@@ -0,0 +1,16 @@
+from pydantic import BaseModel
+from typing import Optional
+from schemas.base import UTCDatetime
+
+
+class PosSettingOut(BaseModel):
+    key: str
+    value: str
+    updated_at: Optional[UTCDatetime] = None
+    updated_by_id: Optional[int] = None
+
+    model_config = {"from_attributes": True}
+
+
+class UpdateSettingRequest(BaseModel):
+    value: str