feat: services, jwt auth, and api controllers

- LeadService with 15 SP calls (CRUD, actividades, pagos, montos)
- UsuarioService for login and profile queries
- JwtService for token generation with claims
- AuthController (login, perfil) with HttpOnly cookie
- LeadController (CRUD, actividades, estado, pago, contacto)
- Registered all services in DI (Program.cs)

backend/src/Ventas.API/Program.cs

@@ -5,6 +5,7 @@ using Microsoft.IdentityModel.Tokens;
 using Ventas.Infrastructure.Data;
 using Ventas.Infrastructure.Repositories;
 using Ventas.Core.Interfaces;
+using Ventas.Services;
 
 var builder = WebApplication.CreateBuilder(args);
 
@@ -21,7 +22,16 @@ builder.Services.AddScoped<ILeadRepository>(sp =>
 builder.Services.AddScoped<ILeadQueryRepository>(sp =>
     new LeadQueryRepository(connectionString));
 
+builder.Services.AddScoped<LeadService>(sp =>
+    new LeadService(connectionString));
+builder.Services.AddScoped<UsuarioService>(sp =>
+    new UsuarioService(connectionString));
+
 var jwtSecret = builder.Configuration["Jwt:Secret"] ?? "default-dev-secret-change-in-production";
+var jwtExpiration = int.Parse(builder.Configuration["Jwt:ExpirationMinutes"] ?? "30");
+builder.Services.AddScoped<JwtService>(sp =>
+    new JwtService(jwtSecret, jwtExpiration));
+
 builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
     .AddJwtBearer(options =>
     {