fix(ci): replace ip route with hostname -I to find DinD subnet

The runner image does not have iproute2 installed, so `ip route` fails
with exit 127. Use `hostname -I` (available everywhere) to get the
container's own IP and derive the /24 prefix for the DinD port scan.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.forgejo/workflows/ci.yml

@@ -55,8 +55,8 @@ jobs:
           # Codeberg's act runner may not register the service container with the
           # 'docker' DNS alias.  Fall back: scan the local /24 subnet for port 2375.
           echo "Docker unreachable via hostname; scanning network for DinD..." >&2
-          GW=$(ip route | awk '/default/{print $3; exit}')
-          PREFIX=$(echo "$GW" | cut -d. -f1-3)
+          MY_IP=$(hostname -I | awk '{print $1}')
+          PREFIX=$(echo "$MY_IP" | cut -d. -f1-3)
           FOUND=""
           for i in $(seq 1 50); do
             ip="${PREFIX}.${i}"