feat(V2): migrazione alpaca completa

Task 6.7: porting alpaca da services/mcp-alpaca a src/cerbero_mcp.
client.py + leverage_cap.py copiati 1:1 (default cap 1 cash).
tools.py: 17 tool senza ACL/Principal/audit. Router /mcp-alpaca con 18
route (env_info + 17 tool). Builder branch alpaca: paper=(env=="testnet"),
api_key viene da settings.alpaca.api_key_id. Test client + leverage_cap
migrati (15 test alpaca pass). Test builder con stub SDK alpaca-py.

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

tests/unit/exchanges/alpaca/test_client.py

@@ -0,0 +1,80 @@
+from __future__ import annotations
+
+from unittest.mock import MagicMock
+
+import pytest
+
+
+@pytest.mark.asyncio
+async def test_init_paper_mode(client, mock_trading):
+    assert client.paper is True
+    assert client._trading is mock_trading
+
+
+@pytest.mark.asyncio
+async def test_get_account_calls_trading(client, mock_trading):
+    mock_trading.get_account.return_value = MagicMock(
+        model_dump=lambda: {"equity": 100000, "cash": 50000}
+    )
+    result = await client.get_account()
+    mock_trading.get_account.assert_called_once()
+    assert result["equity"] == 100000
+
+
+@pytest.mark.asyncio
+async def test_get_positions_returns_list(client, mock_trading):
+    pos_mock = MagicMock(model_dump=lambda: {"symbol": "AAPL", "qty": 10})
+    mock_trading.get_all_positions.return_value = [pos_mock]
+    result = await client.get_positions()
+    assert len(result) == 1
+    assert result[0]["symbol"] == "AAPL"
+
+
+@pytest.mark.asyncio
+async def test_place_market_order_stocks(client, mock_trading):
+    order_mock = MagicMock(model_dump=lambda: {"id": "o123", "symbol": "AAPL"})
+    mock_trading.submit_order.return_value = order_mock
+    result = await client.place_order(
+        symbol="AAPL", side="buy", qty=1, order_type="market", asset_class="stocks",
+    )
+    assert result["id"] == "o123"
+    assert mock_trading.submit_order.called
+
+
+@pytest.mark.asyncio
+async def test_place_limit_order_requires_price(client):
+    with pytest.raises(ValueError, match="limit_price"):
+        await client.place_order(
+            symbol="AAPL", side="buy", qty=1, order_type="limit",
+        )
+
+
+@pytest.mark.asyncio
+async def test_cancel_order(client, mock_trading):
+    mock_trading.cancel_order_by_id.return_value = None
+    result = await client.cancel_order("o1")
+    mock_trading.cancel_order_by_id.assert_called_once_with("o1")
+    assert result == {"order_id": "o1", "canceled": True}
+
+
+@pytest.mark.asyncio
+async def test_close_position_no_options(client, mock_trading):
+    order_mock = MagicMock(model_dump=lambda: {"id": "close-1"})
+    mock_trading.close_position.return_value = order_mock
+    result = await client.close_position("AAPL")
+    assert mock_trading.close_position.called
+    assert result["id"] == "close-1"
+
+
+@pytest.mark.asyncio
+async def test_get_clock(client, mock_trading):
+    clock_mock = MagicMock(model_dump=lambda: {"is_open": True, "next_close": "2026-04-21T20:00:00Z"})
+    mock_trading.get_clock.return_value = clock_mock
+    result = await client.get_clock()
+    assert result["is_open"] is True
+
+
+@pytest.mark.asyncio
+async def test_invalid_asset_class(client):
+    with pytest.raises(ValueError, match="invalid asset_class"):
+        await client.get_ticker("AAPL", asset_class="forex")