Root cause: handleHosts and partitionTargets both declared their result
slices with `var`, so an empty result (no logs old enough yet, or every
requested target blocked by a floor) marshaled to JSON `null` instead of
`[]` on fields without `omitempty`. The frontend's `.length` access on
that `null` threw mid-render, which is why this shipped with the spinner
stuck forever instead of the empty state ever painting -- production is
freshly deployed with nothing yet older than the default 30-day cutoff,
so every user hit this on first load.
Also replaces the static "Loading hosts…" text with the existing
shimmer Skeleton component for real visual feedback, and adds `?? []`
fallbacks in api.ts as a second line of defense.
jcoffey-dev
9e21ea17bb