feat(V2): router deribit + test migrati

Router /mcp-deribit/* monta 34 tool (28 read + 6 write) come endpoint
POST /mcp-deribit/tools/{tool_name}, con DI per env (request.state) e
client (ClientRegistry). Write tools costruiscono creds minimale
{max_leverage, client_id} da settings per leverage cap enforcement.

Test deribit migrati: test_client.py + test_leverage_cap.py riassegnati
sotto tests/unit/exchanges/deribit/ con import rewrite mcp_* -> cerbero_mcp.*.
Skip dei legacy V1-only test_environment_info / test_server_acl / test_env_validation
(ACL e resolve_environment eliminati in V2).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/unit/exchanges/deribit/test_leverage_cap.py

@@ -0,0 +1,50 @@
+from __future__ import annotations
+
+import pytest
+from fastapi import HTTPException
+from cerbero_mcp.exchanges.deribit.leverage_cap import enforce_leverage, get_max_leverage
+
+
+def test_get_max_leverage_returns_creds_value():
+    creds = {"max_leverage": 5}
+    assert get_max_leverage(creds) == 5
+
+
+def test_get_max_leverage_default_when_missing():
+    """Default 1 (cash) se il secret non ha max_leverage."""
+    assert get_max_leverage({}) == 1
+
+
+def test_enforce_leverage_pass_under_cap():
+    creds = {"max_leverage": 3}
+    enforce_leverage(2, creds=creds, exchange="deribit")  # no raise
+
+
+def test_enforce_leverage_pass_at_cap():
+    creds = {"max_leverage": 3}
+    enforce_leverage(3, creds=creds, exchange="deribit")  # no raise
+
+
+def test_enforce_leverage_reject_over_cap():
+    creds = {"max_leverage": 3}
+    with pytest.raises(HTTPException) as exc:
+        enforce_leverage(10, creds=creds, exchange="deribit")
+    assert exc.value.status_code == 403
+    assert exc.value.detail["error"] == "LEVERAGE_CAP_EXCEEDED"
+    assert exc.value.detail["exchange"] == "deribit"
+    assert exc.value.detail["requested"] == 10
+    assert exc.value.detail["max"] == 3
+
+
+def test_enforce_leverage_reject_when_below_one():
+    creds = {"max_leverage": 3}
+    with pytest.raises(HTTPException) as exc:
+        enforce_leverage(0, creds=creds, exchange="deribit")
+    assert exc.value.status_code == 403
+
+
+def test_enforce_leverage_default_when_none():
+    """Se requested è None, applica il cap come default."""
+    creds = {"max_leverage": 3}
+    result = enforce_leverage(None, creds=creds, exchange="deribit")
+    assert result == 3