Add inventory domain foundation

backend/app/inventory/exceptions.py

@@ -0,0 +1,25 @@
+"""Inventory domain exceptions."""
+
+
+class InventoryError(Exception):
+    """Base exception for inventory operations."""
+
+
+class InventoryValidationError(InventoryError):
+    """Raised when an inventory business rule is violated."""
+
+
+class DuplicateAssetID(InventoryError):
+    """Raised when an Asset ID is already assigned to another miner."""
+
+    def __init__(self, asset_id: str):
+        self.asset_id = asset_id
+        super().__init__(f"Asset ID already exists: {asset_id}")
+
+
+class MinerNotFound(InventoryError):
+    """Raised when an inventory miner cannot be found."""
+
+    def __init__(self, miner_id: object):
+        self.miner_id = miner_id
+        super().__init__(f"Miner not found: {miner_id}")