Add POI feature and imporve the overall backend implementation

services/procurement/scripts/demo/seed_demo_purchase_orders.py

@@ -112,8 +112,15 @@ async def create_purchase_order(
     created_at = datetime.now(timezone.utc) + timedelta(days=created_offset_days)
     required_delivery = created_at + timedelta(days=random.randint(3, 7))
 
-    # Generate PO number
-    po_number = f"PO-{datetime.now().year}-{random.randint(100, 999)}"
+    # Generate unique PO number
+    while True:
+        po_number = f"PO-{datetime.now().year}-{random.randint(100, 999)}"
+        # Check if PO number already exists in the database
+        existing_po = await db.execute(
+            select(PurchaseOrder).where(PurchaseOrder.po_number == po_number).limit(1)
+        )
+        if not existing_po.scalar_one_or_none():
+            break
 
     # Calculate amounts
     subtotal = total_amount