fix: Set Gunicorn option forwarded-allow-ips

Currently, the `request.url_for` and `URLPath.make_absolute_url` methods
always build URLs with "http" scheme, even when the original requested
URL is using "https".

The reason for this is that Gunicorn does not allow IPs other than
127.0.0.1 to set secure headers by default. As regular RomM
installations don't know which frontend IPs will try to set security
headers in advance, we can disable this validation, and fix URL
building.

A simple way to test this change is to access any of the `feed` endpoints,
which generate URLs using the mentioned methods. Accessing the endpoint
using "https" scheme must generate "https" URLs.

Reference:
* https://github.com/encode/starlette/issues/538#issuecomment-2054013679
* https://docs.gunicorn.org/en/stable/settings.html#forwarded-allow-ips

docker/init_scripts/init

@@ -52,6 +52,7 @@ start_bin_gunicorn() {
 		--bind=0.0.0.0:5000 \
 		--bind=unix:/tmp/gunicorn.sock \
 		--pid=/tmp/gunicorn.pid \
+		--forwarded-allow-ips="*" \
 		--workers "${GUNICORN_WORKERS:=2}" \
 		main:app &
 }