Mount Tailscale router at /tailscale prefix so all 10 routes resolve
to /api/tailscale/* as expected by middleware, audit logger, and
frontend. Previously 5 routes (status, config, check-connection,
devices, protect-service) resolved to /api/* instead, with config
colliding with the settings route. Strip redundant /tailscale/ prefix
from OAuth routes that were compensating for the missing mount prefix.
Increase default health check timeout from 10s to 20s to reduce false
positives on slower services.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>