libssh: fix big-endian -R forwarding and crash without entropy source

libssh: fix big-endian -R forwarding and crash without entropy source

On big-endian hosts the server parsed every tcpip-forward bind port as
zero and bound an ephemeral port, so -R remote forwarding never carried
a connection. With no usable entropy source the library crashed inside
mbedtls instead of failing cleanly.

Patches 2-4 were sent upstream to the libssh mailing list:
https://archive.libssh.org/libssh/2026-08/0000000.html
https://archive.libssh.org/libssh/2026-08/0000001.html
Patch 1 backports the seed-failure error path they depend on from
upstream master commit ac4b723c.

Signed-off-by: Daniel Golle <redacted>