feat: core inventory API and secure operation routers

backend/schemas.py

@@ -0,0 +1,40 @@
+from pydantic import BaseModel
+from typing import Optional, List
+from datetime import datetime
+
+# --- Items ---
+class ItemBase(BaseModel):
+    name: str
+    category: str
+    barcode: str
+    quantity: float = 0.0
+    min_quantity: float = 1.0
+    image_url: Optional[str] = None
+    labels_data: Optional[str] = None
+
+class ItemCreate(ItemBase):
+    pass
+
+class Item(ItemBase):
+    id: int
+
+    class Config:
+        from_attributes = True
+
+# --- Operations (Check-in/Check-out Validation) ---
+class OperationCreate(BaseModel):
+    barcode: str
+    quantity: float
+    user_id: int
+
+# --- Audit Logs ---
+class AuditLogResponse(BaseModel):
+    id: int
+    timestamp: datetime
+    user_id: int
+    action: str
+    target_item_id: Optional[int]
+    quantity_change: Optional[float]
+
+    class Config:
+        from_attributes = True