Embedding a neodymium magnet inside a forged/melted aluminum enclosure
The melting temperature of a magnet is irrelevant because it loses it's magnetation long before melting.

Have a look at this site and you'll see that the maximum working temperature of neodymium magnets is approx. 230°C for the most heat resistant magnets. This site explains why the magnets get permanently demagnetized by heat.

The only way to embed a magnet into aluminum and keep it intact is to prepare a cavity in the aluminum and insert the magnet later (when the metal cooled down to working temperature). If you want to coat the magnet, either use galvanization or a different material.