rego-tunnel: fix exit 0 causing container restart loop

Changed exit 0 to return 0 in vpn_scripts/start.sh.
When the script is sourced via entrypoint, exit terminates
the parent shell before the Windows VM entry.sh can run.

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/rego-tunnel/vpn_scripts/start.sh

@@ -110,4 +110,4 @@ get_container_ip() {
   echo "[rego-tunnel] SOCKS5 proxy available at $CONTAINER_IP:1080"
 ) &
 
-exit 0
+return 0