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/schemas/tenant.py

@@ -0,0 +1,54 @@
+"""
+Schema Pydantic per tenant (super-admin).
+"""
+
+import uuid
+from datetime import datetime
+from typing import Literal
+
+from pydantic import BaseModel, Field, field_validator
+
+TenantPlanType = Literal["starter", "pro", "enterprise"]
+
+
+class TenantCreateRequest(BaseModel):
+    slug: str = Field(min_length=3, max_length=63, pattern=r"^[a-z0-9-]+$")
+    name: str = Field(min_length=2, max_length=255)
+    plan: TenantPlanType = "starter"
+    max_mailboxes: int = Field(default=5, ge=1, le=1000)
+    max_users: int = Field(default=10, ge=1, le=1000)
+
+    # Utente admin iniziale
+    admin_email: str
+    admin_password: str = Field(min_length=8)
+    admin_full_name: str = Field(min_length=2, max_length=255)
+
+    @field_validator("slug")
+    @classmethod
+    def validate_slug(cls, v: str) -> str:
+        reserved = {"api", "admin", "www", "mail", "smtp", "imap", "pecflow", "app"}
+        if v in reserved:
+            raise ValueError(f"Slug '{v}' riservato")
+        return v.lower()
+
+
+class TenantUpdateRequest(BaseModel):
+    name: str | None = Field(default=None, min_length=2, max_length=255)
+    plan: TenantPlanType | None = None
+    is_active: bool | None = None
+    max_mailboxes: int | None = Field(default=None, ge=1, le=1000)
+    max_users: int | None = Field(default=None, ge=1, le=1000)
+
+
+class TenantResponse(BaseModel):
+    id: uuid.UUID
+    slug: str
+    name: str
+    plan: str
+    is_active: bool
+    max_mailboxes: int
+    max_users: int
+    created_at: datetime
+    updated_at: datetime
+
+    model_config = {"from_attributes": True}