Checks if a string is a valid UUID.

Uses Ecto.UUID.cast/1 for robust validation that handles all UUID formats (v4, v7, etc.).

Examples

iex> PhoenixKit.Utils.UUID.valid?("550e8400-e29b-41d4-a716-446655440000")
true

iex> PhoenixKit.Utils.UUID.valid?("not-a-uuid")
false

iex> PhoenixKit.Utils.UUID.valid?(123)
false