fix: serialize unit subscription to avoid dbus reply cap}
- Replace forEach(async) loop with sequential for...of over unit IDs so getUnit, props, and properties factory calls no longer fan out in parallel
- Prevents bursts on Reloading from exceeding dbus-daemon's max_replies_per_connection=128 limit, which produced ~90+ "max replies reached" warnings per burst
- Invert the filter.isValid check to early-continue and reduce nesting
- Drop the stray empty statement left over from the previous forEach body