Anyway I think the pin with the square pad is pin 01, which would make sense. Also kicad appears to know that it's mounted on the other side of the board
Here’s a 120Ω resistor with that blue LED, looks a little brighter
Can I just say
HOLY FUCKING SHIT IT WORKED ON THE FIRST TRY OMG
Necroposting to CC @jalcine , in case you'd like to see progress pictures
Note to future me: LED long leg go in circle hole