feat(api): List + GetById usuarios — handlers, repo, endpoints [UDT-008]

src/api/SIGCM2.Application/Usuarios/GetById/UsuarioDetailDto.cs

@@ -0,0 +1,17 @@
+namespace SIGCM2.Application.Usuarios.GetById;
+
+/// <summary>
+/// Full detail projection — excludes PasswordHash and PermisosJson (security).
+/// </summary>
+public sealed record UsuarioDetailDto(
+    int Id,
+    string Username,
+    string Nombre,
+    string Apellido,
+    string? Email,
+    string Rol,
+    bool Activo,
+    bool MustChangePassword,
+    DateTime? UltimoLogin,
+    DateTime? FechaModificacion
+);