feat(V2): bearer auth middleware con compare_digest

Implementa install_auth_middleware con whitelist /health /apidocs /openapi.json,
token timing-safe via secrets.compare_digest, request.state.environment injection.
Fix pyproject: --import-mode=prepend (importlib + PEP563 rompe FastAPI Request injection).
Rimosso from __future__ import annotations da test_auth.py per stesso motivo.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/unit/test_auth.py

@@ -0,0 +1,100 @@
+import pytest
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+
+
+def test_health_no_auth_required():
+    from cerbero_mcp.auth import install_auth_middleware
+    fa = FastAPI()
+    install_auth_middleware(fa, testnet_token="t", mainnet_token="m")
+
+    @fa.get("/health")
+    def h():
+        return {"ok": True}
+
+    c = TestClient(fa)
+    r = c.get("/health")
+    assert r.status_code == 200
+
+
+def test_apidocs_no_auth_required():
+    from cerbero_mcp.auth import install_auth_middleware
+    fa = FastAPI(docs_url="/apidocs")
+    install_auth_middleware(fa, testnet_token="t", mainnet_token="m")
+
+    c = TestClient(fa)
+    r = c.get("/apidocs")
+    assert r.status_code == 200
+    r = c.get("/openapi.json")
+    assert r.status_code == 200
+
+
+def test_missing_authorization_header_401():
+    from cerbero_mcp.auth import install_auth_middleware
+    fa = FastAPI()
+    install_auth_middleware(fa, testnet_token="t", mainnet_token="m")
+
+    @fa.get("/mcp-deribit/health")
+    def h():
+        return {"ok": True}
+
+    c = TestClient(fa)
+    r = c.get("/mcp-deribit/health")
+    assert r.status_code == 401
+
+
+def test_invalid_bearer_401():
+    from cerbero_mcp.auth import install_auth_middleware
+    fa = FastAPI()
+    install_auth_middleware(fa, testnet_token="t", mainnet_token="m")
+
+    @fa.get("/mcp-deribit/health")
+    def h():
+        return {"ok": True}
+
+    c = TestClient(fa)
+    r = c.get("/mcp-deribit/health", headers={"Authorization": "Bearer wrong"})
+    assert r.status_code == 401
+
+
+def test_testnet_token_sets_env_testnet():
+    from cerbero_mcp.auth import install_auth_middleware
+    from fastapi import Request
+
+    fa = FastAPI()
+    install_auth_middleware(fa, testnet_token="tk_test", mainnet_token="tk_live")
+
+    @fa.get("/mcp-deribit/peek")
+    def peek(request: Request):
+        return {"env": request.state.environment}
+
+    c = TestClient(fa)
+    r = c.get("/mcp-deribit/peek", headers={"Authorization": "Bearer tk_test"})
+    assert r.status_code == 200
+    assert r.json() == {"env": "testnet"}
+
+
+def test_mainnet_token_sets_env_mainnet():
+    from cerbero_mcp.auth import install_auth_middleware
+    from fastapi import Request
+
+    fa = FastAPI()
+    install_auth_middleware(fa, testnet_token="tk_test", mainnet_token="tk_live")
+
+    @fa.get("/mcp-deribit/peek")
+    def peek(request: Request):
+        return {"env": request.state.environment}
+
+    c = TestClient(fa)
+    r = c.get("/mcp-deribit/peek", headers={"Authorization": "Bearer tk_live"})
+    assert r.status_code == 200
+    assert r.json() == {"env": "mainnet"}
+
+
+def test_uses_compare_digest():
+    """Verifica che _check_token usi secrets.compare_digest (timing-safe)."""
+    import inspect
+    from cerbero_mcp import auth
+
+    src = inspect.getsource(auth)
+    assert "compare_digest" in src, "auth.py deve usare secrets.compare_digest"