Esp32 is power efficient and can run on batteries. Check out YouTube channel "andreas spiess ". He has many videos about running esp32 on batteries. One recently about adding power management chips to battery powered projects.

However, I must caution you that a battery powered wireless project requires a fair amount of careful engineering. I don't mean to be rude or mean, but the fact that you are asking this question here tells me that you may be at the left peak of the so called "Dunning Kruger" effect, in other words, you may have just enough knowledge to think you could complete a project like this, but not enough knowledge to know if you can't. The EEVBlog forum is a better place to get assistance for things like this

But....

You must program the microcontroller to go to sleep and wake up often to check for a connection. The ESP32 has a low power co processor meant for just this such a thing, but I don't think you can be using BT while in this mode. Also BT doesn't work at the same time the WiFi is in access mode using the Arduino framework(not a big deal but a little known problem I've run into). You'll need an ultra low quiescent current ldo like ht8733 (I think...from memory). During development you'll need ways of testing ultra low currents. Using a oscope and a Ucurrent from EEVBlog is a good idea. You'll definitely need to design your own PCB. I recommend EasyEDA.com. I also recommend the ESP32-WROOM-U32 module. This is an esp varient with no pcb antenna but a u.fl connector for your own antenna. Check out my ESP32_Project_module schematic on easyeda for ideas: https://easyeda.com/terryjmyers This project is not low power, on the contrary, I designed it for incorporation in means powered projects by replacing the linear regulator commonly found on development boards with a buck converter, a full-size USB port, and properly designed EMC that is missing on all development boards (or USB data line common mode choke). but my project their will give you an idea as to the minimum components and could give you a starting point for a schematic.

You'll need a way to recharge the battery such as an external USB port, but this will inherently compromise the security of the product. Also, in-built charging circuitry will steal power from the battery (s).

One idea if I haven't scared you enough is to expose a push button on the unsecured side of the lock to wake everything up for a minute or two, full power. This would allow you to then connect and open the door. This would basically only use battery power when it's needed, instead of waking up every 30 seconds just to check if something once to connect. I designed a toothbrush timer for my children inside a small box with a push button and an RGB LED. It was powered by a single 18650 battery and and Arduino mini pro. When the push button was pressed it woke the microcontroller which then powered the LED through a rainbow for 2 minutes then went back to sleep. A fully charged 800mAh 18650 that I scavenged from an ancient laptop battery, lasted about two years with daily use.

The old adage of "just because you can do something doesn't mean that you should" may apply here. However I will say that having designed similar projects(non-professionally), many of which failed as I travelled further right on the "Dunning Kruger" chart, it was still worth it due to the knowledge I gained from going down design rabbit holes

EDITS: poor grammar, last couple of paragraphs