Which heir to the throne of the French kingdom was the last to hold the traditional title of Dauphin?

Louis Antoine was heir to Charles X and became King of France (as Louis XIX) on 2 August 1830. Not very long, just some 20 minutes. But still - King of France. He was the last to bear the title of a Dauphin.

https://en.wikipedia.org/wiki/Dauphin_of_France

In September 1824, Charles X succeeded his brother Louis XVIII as King of France, with his son Louis Antoine, Duke of Angoulême, assuming the title of Dauphin, the traditional title used by the heir apparent to the French throne. However, six years later, in 1830, Charles X was forced to abdicate in what became known as the July Revolution, and was succeeded not by the Dauphin, but instead by his cousin Louis Philippe, Duke of Orléans. As Louis Philippe I, the new king elected to move away from the traditional forms and titles of the Ancien Régime; he took the title "King of the French" rather than "King of France", while the term "Prince Royal" rather than "Dauphin" was used to refer to Louis Philippe's eldest son and heir, Ferdinand Philippe. Following the restoration of the Bonapartist Empire in 1852, the eldest son and heir of Napoleon III was referred to as "Prince Imperial" until the final end of the French monarchy in 1870.

https://en.wikipedia.org/wiki/Dauphin_of_France
https://en.wikipedia.org/wiki/Louis_Antoine,_Duke_of_Angoul%C3%AAme
https://en.wikipedia.org/wiki/Ferdinand_Philippe,_Duke_of_Orl%C3%A9ans
https://en.wikipedia.org/wiki/Napol%C3%A9on,_Prince_Imperial