netbird: update to 0.53.0 with config fix

netbird: update to 0.53.0 with config fix

changelog: https://github.com/netbirdio/netbird/releases/tag/v0.53.0

Update init file to include `NB_CONFIG="/etc/netbird/config.json"`
variable, ensuring configuration compatibility as before (fixes issue
introduced by profiles feature in 0.52.2). Existing configurations remain
compatible.

Note: license for some components (`management`, `relay`, `signal`) changed
to **AGPLv3**. These components aren't packaged for OpenWrt, so there's no
immediate effect, but record the change for future reference.

Signed-off-by: Wesley Gimenes <redacted>