BPI-SINOVOIP/BPI-R3MINI-OPENWRT-V21.02.3 ? reverse-engineered prompt

Build me a working OpenWrt firmware build setup for the Banana Pi BPI R3 Mini using this repository.

I want to be able to fetch the package feeds, choose the right device and options in the config menu, and build a flashable firmware image without having to figure out all the OpenWrt steps myself. Please make it easy to repeat the build, and include any helpful defaults for a router style device, like network basics and the web interface if that fits.

If anything is missing or the build needs a newer or different package source, look up the current OpenWrt docs online and adjust it so the build succeeds. After that, give me a simple way to run the build again later and a short note on what files to flash to the device.