fix: Create certs as 1000 user

[holzeis]

Also generates the certs on the default path so that the certs directory doesn't have to be set if the default certs should be used.

tested locally with the following

mkdir data

docker run \
  --name webapp \
  --rm \
  -v ./data:/data \
  -p 3001:3001 -it \
ghcr.io/holzeis/webapp:0.1.2  \
  --coordinator-endpoint=021025118ede915d626f7da184d75af7281dca965dd91a06993cf9d21fe4ca54e5@34.89.166.156:9045 \
  --data-dir=/data \
  --esplora=http://api.10101.finance:3000 \
  mainnet

[bonomat]

Thank you!