This is a really intriguing concept! I really like tower defence games, and combining it with poker hands is a great idea that works really well. I'd have liked a slightly steeper difficulty curve, but this is a whole lot of fun so far!
I had the same issue as Magn below in being unable to lock cards on redraw, which meant it was usually better for me to focus on placing more towers rather than upgrading except where I had a high card only.
From reading over your devlog it looks like we've used a really similar Music system! Yours is really well implemented, and the music choices were great. Also, the clicking sound effect for damage is really satisfying for some reason, love it.
I also just wanted to say that I really enjoyed reading your devlog - it's always great to get details on how people approach programming, and yours was particularly thorough.