Fixed 'Cannot redeclare Producto::Search2()' fatal error by
removing the duplicate function at line 778. The first Search2()
function (line 664) is the correct one with proper search
functionality including JOIN with proveedor table.
Fixed 'Undefined variable $pages' error when no search criteria
are provided in Search3(), Search2(), and SearchDuplicados()
functions by initializing $pages array with proper pagination
structure in the else blocks.
