GET /api/customers gains a summary object (total/online/depleted/
depletingSoon/disabled/enabled) computed server-side; the customers page
renders it as a six-cell stats strip above the toolbar.
Predicates aligned verbatim with 3x-ui client_paging.go:
- depleted = (limit>0 && used>=limit) || (expiry set && expiry<=now),
counted regardless of status;
- depletingSoon = active && !depleted && (expiry within expireDiff days
|| remaining traffic < trafficDiff GB), thresholds from new settings
expireDiff/trafficDiff with 3x-ui's factory default 0 (nobody counts
until configured);
- enabled = status active; disabled = manual suspensions only.
Online reuses the existing 3-minute presence projection.
Golden diff confined to the additive summary keys; summary_test.go
covers every bucket with thresholds off (soon=0) and on (soon=2).
