Why do people always prefix every food I make with "vegan"?

Because traditionally both of those recipes are not vegan? Chili is meat based and pumpkin bread has eggs. You didn't make chili and pumpkin bread, you changed the recipes. They feel the need to indicate that somehow.

I don't know your family, so I don't know if they're doing it to be annoying, I guess if they're also calling your salads vegan salads, that would answer the question, but I don't see any harm in them labeling the vegan food you make as vegan food. They still eat it right? They're not shit talking it for being vegan are they?

I get it. I realized I was doing a similar thing with LGBTQ+ stuff. I thought I was inclusive minded, but after using Lemmy for awhile and a few interactions I realized I still had some level of mental partitioning. It was only apparent in my internal reaction to adult content that was not my brand. So I have actively pursued nominal inclusion in my interactions and more critically assess my biases.

I appreciate knowing when a dish is vegan because it tells me that it is non dairy which is my main concern. Outside of that context it is absolutely a prejudiced label in most cases. Perhaps try naming your own dishes in some unique way and not using traditional names so that someone must be more overt in prejudice to add a label of vegan to the name.

It's a form of 'othering', which is an attempt to portray something (we don't associate with) as fundamentally different or alien.

It probably stems from their cognitive dissonance, as in you're eating cruelty-free and they're not, so it helps them resolve any mental tension about their cruelty-containing diet by painting yours as strange.

If I were in your shoes, I'd sort out what I make of their behaviour. Are they good-naturedly adjusting to a family member making a lifestyle change or are they trolling. If I felt they were trolling, I'd do the opposite of what they're doing. I would insist on labelling everything that is naturally vegan, "A vegan [food item, like watermelon]" and correct them each time, etc. To push it a step further, which would likely be too trolling for my tastes, call non-vegan things something like "animal cruelty [food item, like pumpkin break]"

Being vegan - interacting with omnivores and their denialism, projections, etc. - gets much easier with time.

Edit: Another approach would be to non-judgementally ask them about it, which might help them discover their own motivations and feelings around the issue. "I notice you're prefixing, and I'd like to understand why you feel the need to do that better. Can you tell me a little more about what's going on for you?"