Add risk management features: implement KillSwitch and StopConditionsGuard; update settings and tests

tests/unit/test_kill_switch.py

@@ -0,0 +1,27 @@
+from __future__ import annotations
+
+from arbitrade.risk.kill_switch import KillSwitch
+
+
+def test_kill_switch_can_activate_and_deactivate() -> None:
+    kill_switch = KillSwitch()
+
+    assert not kill_switch.is_active
+    assert kill_switch.reason is None
+
+    kill_switch.activate(reason="manual")
+
+    assert kill_switch.is_active
+    assert kill_switch.reason == "manual"
+
+    kill_switch.deactivate()
+
+    assert not kill_switch.is_active
+    assert kill_switch.reason is None
+
+
+def test_kill_switch_active_on_init_sets_reason() -> None:
+    kill_switch = KillSwitch(active=True)
+
+    assert kill_switch.is_active
+    assert kill_switch.reason == "manual"