feat(V2): migrazione macro completa (read-only, env ignored)

- exchanges/macro: cot.py + cot_contracts.py + fetchers.py copiati 1:1 con
  rewrite import mcp_common -> cerbero_mcp.common, mcp_macro -> cerbero_mcp.exchanges.macro
- nuovo MacroClient stateless wrapper: trasporta solo fred_api_key/finnhub_api_key,
  niente HTTP session (i fetchers usano async_client ad-hoc)
- tools.py: 11 tool (get_treasury_yields, get_yield_curve_slope,
  get_breakeven_inflation, get_economic_indicators, get_macro_calendar,
  get_market_overview, get_equity_futures, get_asset_price, get_cot_tff,
  get_cot_disaggregated, get_cot_extreme_positioning) — niente write,
  niente leverage_cap
- routers/macro.py: prefix /mcp-macro, 11 route POST /tools/*
- builder branch macro: stesse credenziali per testnet/mainnet (env ignorato);
  registry istanzia 2 entry, costo trascurabile (wrapper stateless)
- test migrati: test_cot.py + test_fetchers.py (test_server_acl.py skippato V1-only)
- nuovo test test_build_client_macro_no_env_distinction in test_exchanges_builder.py

Suite: 224 passed.

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

tests/unit/test_exchanges_builder.py

@@ -102,6 +102,29 @@ async def test_build_client_alpaca_returns_correct_env(monkeypatch):
     assert c_live.paper is False
 
 
+@pytest.mark.asyncio
+async def test_build_client_macro_no_env_distinction(monkeypatch):
+    from tests.unit.test_settings import _minimal_env
+
+    for k, v in _minimal_env().items():
+        monkeypatch.setenv(k, v)
+
+    from cerbero_mcp.settings import Settings
+    from cerbero_mcp.exchanges import build_client
+    from cerbero_mcp.exchanges.macro.client import MacroClient
+
+    s = Settings()
+    c_test = await build_client(s, "macro", "testnet")
+    c_live = await build_client(s, "macro", "mainnet")
+
+    # entrambi sono MacroClient validi (env ignorato)
+    assert isinstance(c_test, MacroClient)
+    assert isinstance(c_live, MacroClient)
+    # Stesse credenziali (env ignorato)
+    assert c_test.fred_api_key == c_live.fred_api_key
+    assert c_test.finnhub_api_key == c_live.finnhub_api_key
+
+
 @pytest.mark.asyncio
 async def test_build_client_unknown_exchange_raises(monkeypatch):
     from tests.unit.test_settings import _minimal_env