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/app/core/security.py

@@ -0,0 +1,158 @@
+"""
+Modulo sicurezza – cifratura AES-256-GCM, hashing password, JWT utilities.
+
+ADR-002: Le credenziali IMAP/SMTP vengono cifrate con AES-256-GCM prima di
+essere scritte in DB. La chiave è in variabile d'ambiente (ENCRYPTION_KEY).
+Formato storage: base64(nonce_12byte || ciphertext || tag_16byte)
+"""
+
+import base64
+import os
+from datetime import UTC, datetime, timedelta
+from typing import Any
+from uuid import UUID
+
+import bcrypt as _bcrypt
+from cryptography.hazmat.primitives.ciphers.aead import AESGCM
+from jose import JWTError, jwt
+
+from app.config import get_settings
+
+settings = get_settings()
+
+# ─── Password hashing (bcrypt diretto, compatibile con bcrypt 4.x/5.x) ───────
+_BCRYPT_ROUNDS = 12
+
+
+def hash_password(password: str) -> str:
+    """Genera hash bcrypt della password (work factor 12)."""
+    pwd_bytes = password.encode("utf-8")
+    salt = _bcrypt.gensalt(rounds=_BCRYPT_ROUNDS)
+    return _bcrypt.hashpw(pwd_bytes, salt).decode("utf-8")
+
+
+def verify_password(plain_password: str, hashed_password: str) -> bool:
+    """Verifica password contro il suo hash."""
+    try:
+        return _bcrypt.checkpw(
+            plain_password.encode("utf-8"),
+            hashed_password.encode("utf-8"),
+        )
+    except Exception:
+        return False
+
+
+# ─── JWT ──────────────────────────────────────────────────────────────────────
+def create_access_token(
+    subject: str | UUID,
+    tenant_id: str | UUID,
+    role: str,
+    extra_claims: dict[str, Any] | None = None,
+) -> str:
+    """
+    Crea un JWT access token con scadenza configurabile.
+
+    Claims standard:
+      - sub: user_id (string)
+      - tid: tenant_id
+      - role: ruolo utente
+      - exp: scadenza
+      - iat: emesso a
+    """
+    now = datetime.now(UTC)
+    expire = now + timedelta(minutes=settings.access_token_expire_minutes)
+
+    payload: dict[str, Any] = {
+        "sub": str(subject),
+        "tid": str(tenant_id),
+        "role": role,
+        "iat": now,
+        "exp": expire,
+        "type": "access",
+    }
+    if extra_claims:
+        payload.update(extra_claims)
+
+    return jwt.encode(payload, settings.secret_key, algorithm=settings.algorithm)
+
+
+def create_refresh_token(subject: str | UUID, tenant_id: str | UUID) -> str:
+    """
+    Crea un JWT refresh token con scadenza lunga (30 giorni default).
+    Non contiene il ruolo – viene rivalutato a ogni refresh.
+    """
+    now = datetime.now(UTC)
+    expire = now + timedelta(days=settings.refresh_token_expire_days)
+
+    payload: dict[str, Any] = {
+        "sub": str(subject),
+        "tid": str(tenant_id),
+        "iat": now,
+        "exp": expire,
+        "type": "refresh",
+    }
+    return jwt.encode(payload, settings.secret_key, algorithm=settings.algorithm)
+
+
+def decode_token(token: str) -> dict[str, Any]:
+    """
+    Decodifica e valida un JWT token.
+    Solleva JWTError se il token è invalido o scaduto.
+    """
+    return jwt.decode(token, settings.secret_key, algorithms=[settings.algorithm])
+
+
+def is_token_valid(token: str, expected_type: str = "access") -> bool:
+    """Verifica rapidamente la validità del token senza sollevare eccezioni."""
+    try:
+        payload = decode_token(token)
+        return payload.get("type") == expected_type
+    except JWTError:
+        return False
+
+
+# ─── AES-256-GCM cifratura credenziali (ADR-002) ─────────────────────────────
+def encrypt_credential(plaintext: str) -> str:
+    """
+    Cifra una stringa con AES-256-GCM usando la chiave applicativa.
+
+    Formato output: base64(nonce_12byte || ciphertext || tag_16byte)
+    Il tag GCM (16 byte) è automaticamente concatenato al ciphertext da AESGCM.
+    """
+    key = settings.encryption_key_bytes
+    aesgcm = AESGCM(key)
+    nonce = os.urandom(12)  # 12 byte nonce raccomandato per GCM
+
+    # AESGCM.encrypt() restituisce ciphertext + tag concatenati
+    ciphertext_with_tag = aesgcm.encrypt(nonce, plaintext.encode("utf-8"), None)
+
+    # Concatena nonce + ciphertext_with_tag e codifica in base64
+    raw = nonce + ciphertext_with_tag
+    return base64.b64encode(raw).decode("ascii")
+
+
+def decrypt_credential(encrypted: str) -> str:
+    """
+    Decifra una stringa cifrata con encrypt_credential().
+    Solleva ValueError se la decifratura fallisce (chiave errata o dati corrotti).
+    """
+    key = settings.encryption_key_bytes
+    aesgcm = AESGCM(key)
+
+    try:
+        raw = base64.b64decode(encrypted.encode("ascii"))
+        nonce = raw[:12]
+        ciphertext_with_tag = raw[12:]
+        plaintext_bytes = aesgcm.decrypt(nonce, ciphertext_with_tag, None)
+        return plaintext_bytes.decode("utf-8")
+    except Exception as e:
+        raise ValueError(f"Decifratura fallita: {e}") from e
+
+
+# ─── Hash sicuro per refresh token storage ────────────────────────────────────
+import hashlib
+
+
+def hash_token(token: str) -> str:
+    """SHA-256 del token raw per storage sicuro in DB."""
+    return hashlib.sha256(token.encode("utf-8")).hexdigest()