feat: introduce training module with new entities, migrations, API, and frontend application, and add article type and validity days.

src/backend/Zentral.Domain/Entities/Articolo.cs

@@ -24,8 +24,21 @@ public class Articolo : BaseEntity
     public string? MimeType { get; set; }
     public string? Note { get; set; }
     public bool Attivo { get; set; } = true;
+    public int? GiorniValidita { get; set; }
+
+    /// <summary>
+    /// Classificazione specifica dell'articolo (Standard, Corso, Servizio)
+    /// </summary>
+    public TipoArticolo Tipo { get; set; } = TipoArticolo.Standard;
 
     public TipoMateriale? TipoMateriale { get; set; }
     public CodiceCategoria? Categoria { get; set; }
     public ICollection<EventoDettaglioPrelievo> DettagliPrelievo { get; set; } = new List<EventoDettaglioPrelievo>();
 }
+
+public enum TipoArticolo
+{
+    Standard = 0,
+    Corso = 1,
+    Servizio = 2
+}

src/backend/Zentral.Domain/Entities/Cliente.cs

@@ -28,4 +28,5 @@ public class Cliente : BaseEntity
 
     public ICollection<Evento> Eventi { get; set; } = new List<Evento>();
     public ICollection<Zentral.Domain.Entities.Sales.SalesOrder> SalesOrders { get; set; } = new List<Zentral.Domain.Entities.Sales.SalesOrder>();
+    public ICollection<ClienteContatto> Contatti { get; set; } = new List<ClienteContatto>();
 }

src/backend/Zentral.Domain/Entities/ClienteContatto.cs

@@ -0,0 +1,12 @@
+namespace Zentral.Domain.Entities;
+
+public class ClienteContatto : BaseEntity
+{
+    public string Nome { get; set; } = string.Empty;
+    public string Cognome { get; set; } = string.Empty;
+    public string? Email { get; set; }
+    public string? Ruolo { get; set; }
+    public string? Telefono { get; set; }
+    public int ClienteId { get; set; }
+    public Cliente Cliente { get; set; } = null!;
+}

src/backend/Zentral.Domain/Entities/Training/TrainingRecord.cs

@@ -0,0 +1,39 @@
+using System;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace Zentral.Domain.Entities.Training;
+
+public enum TrainingStatus
+{
+    Valid,
+    Expiring,
+    Expired
+}
+
+public class TrainingRecord : BaseEntity
+{
+    public int ClienteContattoId { get; set; }
+    public ClienteContatto ClienteContatto { get; set; } = null!;
+
+    public int ArticoloId { get; set; }
+    public Articolo Articolo { get; set; } = null!;
+
+    public DateTime DataEsecuzione { get; set; }
+    public DateTime? DataScadenza { get; set; }
+    
+    public string? AttestatoUrl { get; set; }
+    public string? Note { get; set; }
+
+    [NotMapped]
+    public TrainingStatus Stato 
+    { 
+        get 
+        {
+            if (!DataScadenza.HasValue) return TrainingStatus.Valid; // Or unknown? Assuming valid if no expiration.
+            var days = (DataScadenza.Value - DateTime.Today).TotalDays;
+            if (days < 0) return TrainingStatus.Expired;
+            if (days <= 30) return TrainingStatus.Expiring;
+            return TrainingStatus.Valid;
+        }
+    }
+}