feat: add secure agent enrollment

backend/app/agent_enrollment/exceptions.py

@@ -0,0 +1,21 @@
+"""Domain exceptions for secure Agent enrollment."""
+
+
+class AgentEnrollmentError(Exception):
+    """Base Agent enrollment error."""
+
+
+class AgentEnrollmentNotFound(AgentEnrollmentError):
+    """The requested Site or Agent Zone does not exist."""
+
+
+class AgentEnrollmentConflict(AgentEnrollmentError):
+    """The requested enrollment conflicts with current Agent routing state."""
+
+
+class AgentEnrollmentTokenInvalid(AgentEnrollmentError):
+    """The supplied bootstrap token cannot be redeemed."""
+
+
+class AgentEnrollmentCredentialCollision(AgentEnrollmentError):
+    """A generated machine credential collided with an existing credential."""