PALM HARBOR — The first smell was lemon. At least she thought it was lemon. Barbara Walker hadn’t smelled a thing in 34 years. Then, on a spring afternoon, she stood on her patio by the pool and caught a whiff of hope. The light was low, the air warm. A sticky breeze ruffled the cypress trees. In the aviary outside the sliding doors, her rescued pigeons were cooing. Walker, then 55, had just .