harry potter - Did Voldemort actually curse the job of Defense Against Dark Arts professor after being denied the position?

So, everyone and their formidable Grandmother believes that DADA position at Hogwarts is cursed so that anyone taking it only lasts a year at most.

Some people who know more than others, might believe that this is because it was cursed by Voldemort after Dumbledore denied him that position (see HBP).

Did Voldemort actually curse the job of Defense Against Dark Arts professor after being denied the position?

As in, is there a canonical/JKR proof/confirmation that it was, indeed, the actual cause from him, as opposed to a plausible conspiracy theory held by everyone in Potterverse with zero proof?

Answer

Yes, the job was definitely cursed.

There have been several interviews with J.K. Rowling where she states that Voldemort has jinxed the job as a point-of-fact. I don’t recall it being explicitly stated in the books (Voldemort never admits to such a curse), except for Dumbledore’s guess in Half-Blood Prince.

An interview shortly after the publication of Deathly Hallows confirms that it was broken with Voldemort’s death, which only makes sense if there was a jinx to break:

Do Ron or Hermione or Harry ever return to Hogwarts in any capacity?

Well, I can well imagine Harry returning to give the odd talk on– on Defense Against the Dark Arts. And – I – and, of course, the jinx is broken now because Voldemort's gone. Now they can keep a good Defense Against the Dark Arts teacher from here on in. So that aspect of the – of the wizarding education is now provided for.

— J.K. Rowling One-On-One: Part One with NBC (July 2007)

Another interview explicitly states that the job was cursed, and also provides part of the inspiration for the curse:

And Defence Against the Dark Arts was also fun because every year you had a new teacher. For the older members of the audience they will remember the Spinal Tap drummer … and … some of you do, clearly. (laughs) Well, when I planned the books I thought that every year we'll have a different Defence Against the Dark Arts teacher, because the job was cursed, as you know.

— J.K. Rowling answers questions at the White House Easter Egg roll (April 2010)

For those, like me, who didn’t get the reference: Spinal Tap is a fictional heavy metal band with a long list of drummers who all died in mysterious circumstances (spontaneous combustion, choked on vomit, eaten by a pet, and so on). A full list of bizarre deaths is on their Wikipedia page.