Fix CI DinD networking: host network mode + curl timeout

The previous fix (container IP resolution) still failed because the
CI runner and compose containers are on separate Docker networks.

- Add docker-compose.ci.yml override with network_mode: host so the
  container shares the runner's network stack directly
- Add --connect-timeout 2 to curl in wait-for-healthy.sh so it fails
  fast instead of hanging indefinitely on unreachable hosts
- Cap health check at 30s (server boots in 5-10s)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ci/wait-for-healthy.sh

@@ -10,7 +10,7 @@ MAX_RETRIES="${2:-60}"
 
 echo "Waiting for ${HOST} to be healthy..."
 for i in $(seq 1 "$MAX_RETRIES"); do
-  if curl -sf "${HOST}/api/v1/auth/login" -o /dev/null 2>/dev/null; then
+  if curl -sf --connect-timeout 2 "${HOST}/api/v1/auth/login" -o /dev/null 2>/dev/null; then
     echo "Server healthy after ${i}s"
     exit 0
   fi