feat: Fase 1 – Fondamenta complete (backend FastAPI + auth + permessi)

- docker-compose.yml: PostgreSQL 16, Redis 7, MinIO, Nginx
- backend FastAPI: struttura monorepo, config pydantic-settings
- modelli SQLAlchemy: tutti i modelli (tenants, users, mailboxes, messages, archival, permissions, labels, audit_log)
- migrazione Alembic 0001: schema completo in pure SQL
- auth API: login JWT, refresh token rotation, logout, 2FA TOTP (setup/verify/disable)
- CRUD utenti: lista, crea, modifica, reset password, soft delete
- permessi granulari (Fase 1-A): mailbox_permissions, assegna/revoca/lista
- CRUD tenant: gestione super-admin
- sicurezza: AES-256-GCM cifratura credenziali IMAP/SMTP, bcrypt password
- RLS PostgreSQL: isolamento multi-tenant per request
- seed sviluppo: tenant demo + admin + operator
- test unit: security (bcrypt, JWT, AES), auth_service
- test integration: auth endpoints, users endpoints
- CI GitHub Actions: lint (ruff), test (pytest), build Docker, security scan
- infra: nginx.conf, redis.conf
- Makefile con comandi make dev/test/migrate/seed

Definition of Done:
✅ Login, refresh token e TOTP funzionanti
✅ make dev porta in piedi tutto lo stack locale
✅ CI configurata

backend/tests/unit/test_security.py

@@ -0,0 +1,143 @@
+"""
+Test unitari per app.core.security.
+"""
+
+import os
+import pytest
+
+# Override variabili d'ambiente per i test (prima di importare app)
+os.environ["ENCRYPTION_KEY"] = "a" * 64
+os.environ["SECRET_KEY"] = "test-secret-key-for-unit-tests-only"
+os.environ["DATABASE_URL"] = "postgresql+asyncpg://test:test@localhost:5432/test"
+os.environ["DATABASE_URL_SYNC"] = "postgresql://test:test@localhost:5432/test"
+
+from app.core.security import (
+    hash_password,
+    verify_password,
+    create_access_token,
+    create_refresh_token,
+    decode_token,
+    encrypt_credential,
+    decrypt_credential,
+    hash_token,
+)
+
+
+class TestPasswordHashing:
+    def test_hash_password_returns_bcrypt_hash(self):
+        hashed = hash_password("MySecurePassword1!")
+        assert hashed.startswith("$2b$")
+        assert len(hashed) > 20
+
+    def test_verify_correct_password(self):
+        password = "MySecurePassword1!"
+        hashed = hash_password(password)
+        assert verify_password(password, hashed) is True
+
+    def test_verify_wrong_password(self):
+        hashed = hash_password("CorrectPassword1!")
+        assert verify_password("WrongPassword1!", hashed) is False
+
+    def test_hash_is_different_each_time(self):
+        """Bcrypt usa salt casuale: due hash dello stesso secret sono diversi."""
+        p = "SamePassword1!"
+        h1 = hash_password(p)
+        h2 = hash_password(p)
+        assert h1 != h2
+        # Ma entrambi verificano correttamente
+        assert verify_password(p, h1)
+        assert verify_password(p, h2)
+
+
+class TestJWT:
+    def test_create_and_decode_access_token(self):
+        import uuid
+        user_id = uuid.uuid4()
+        tenant_id = uuid.uuid4()
+        token = create_access_token(
+            subject=user_id,
+            tenant_id=tenant_id,
+            role="admin",
+        )
+        payload = decode_token(token)
+        assert payload["sub"] == str(user_id)
+        assert payload["tid"] == str(tenant_id)
+        assert payload["role"] == "admin"
+        assert payload["type"] == "access"
+
+    def test_create_and_decode_refresh_token(self):
+        import uuid
+        user_id = uuid.uuid4()
+        tenant_id = uuid.uuid4()
+        token = create_refresh_token(subject=user_id, tenant_id=tenant_id)
+        payload = decode_token(token)
+        assert payload["sub"] == str(user_id)
+        assert payload["type"] == "refresh"
+
+    def test_expired_token_raises(self):
+        from datetime import UTC, datetime, timedelta
+        from jose import jwt
+        from app.config import get_settings
+        from jose import JWTError
+
+        settings = get_settings()
+        payload = {
+            "sub": "user-id",
+            "tid": "tenant-id",
+            "type": "access",
+            "exp": datetime.now(UTC) - timedelta(seconds=1),  # già scaduto
+        }
+        token = jwt.encode(payload, settings.secret_key, algorithm=settings.algorithm)
+        with pytest.raises(JWTError):
+            decode_token(token)
+
+    def test_invalid_signature_raises(self):
+        from jose import JWTError
+        with pytest.raises(JWTError):
+            decode_token("this.is.not.a.valid.token")
+
+
+class TestAESEncryption:
+    def test_encrypt_decrypt_roundtrip(self):
+        secret = "imap_password_super_secret_123!"
+        encrypted = encrypt_credential(secret)
+        decrypted = decrypt_credential(encrypted)
+        assert decrypted == secret
+
+    def test_encrypt_produces_different_output_each_time(self):
+        """Nonce casuale garantisce che due cifrature dello stesso plaintext siano diverse."""
+        secret = "same_secret"
+        enc1 = encrypt_credential(secret)
+        enc2 = encrypt_credential(secret)
+        assert enc1 != enc2
+        # Ma entrambi decifrano correttamente
+        assert decrypt_credential(enc1) == secret
+        assert decrypt_credential(enc2) == secret
+
+    def test_decrypt_with_wrong_data_raises(self):
+        with pytest.raises(ValueError):
+            decrypt_credential("dGhpcyBpcyBub3QgdmFsaWQgYWVzIGRhdGE=")
+
+    def test_encrypt_empty_string(self):
+        encrypted = encrypt_credential("")
+        decrypted = decrypt_credential(encrypted)
+        assert decrypted == ""
+
+    def test_encrypt_unicode_string(self):
+        secret = "pàssword_con_àccenti_è_ù!"
+        encrypted = encrypt_credential(secret)
+        decrypted = decrypt_credential(encrypted)
+        assert decrypted == secret
+
+
+class TestHashToken:
+    def test_hash_is_deterministic(self):
+        token = "my_refresh_token"
+        assert hash_token(token) == hash_token(token)
+
+    def test_different_tokens_different_hashes(self):
+        assert hash_token("token1") != hash_token("token2")
+
+    def test_hash_is_64_chars(self):
+        """SHA-256 produce 32 bytes = 64 caratteri hex."""
+        assert len(hash_token("any_token")) == 64