feat(inbounds): bulk-select clients + UX polish

- ClientBulkModal: add `comment` and VLESS `reverseTag` fields so the
  bulk-add modal can set them on every generated client (matching the
  single-client form)
- ClientRowTable: add multi-select checkboxes (desktop + mobile) with a
  tri-state select-all and a sticky bulk-action bar; emits a new
  `delete-clients` event so the parent can wipe the picked clients in
  one go. Hidden entirely when the inbound has only one client (the
  last one must stay)
- ClientRowTable: new "Remained" column shows live remaining quota
  per client (∞ for unlimited, red when depleted)
- InboundInfoModal: Remained cell now shows the ∞ tag when the client
  has no totalGB limit, matching how Total Usage already renders it
- InboundsPage: add Online tag (+ per-bucket popovers listing client
  emails) to the summary card so it mirrors the per-inbound row, and
  wire an `onDeleteClients` handler that loops the existing single-
  delete endpoint then refreshes once
- InboundList: forward the `delete-clients` event; hide empty remarks
  on both the desktop table (custom #bodyCell) and the mobile card
- useInbounds: aggregate an `online` email list across all inbounds
  so the summary popover has data to render

frontend/src/pages/inbounds/InboundInfoModal.vue

@@ -387,6 +387,9 @@ const showSubscriptionTab = computed(
                 <td>
                   <a-tag v-if="clientStats && clientSettings.totalGB > 0" :color="statsColor(clientStats)">{{
                     getRemainingStats() }}</a-tag>
+                  <a-tag v-else-if="!clientSettings.totalGB || clientSettings.totalGB <= 0" color="purple">
+                    <InfinityIcon />
+                  </a-tag>
                 </td>
                 <td>
                   <a-tag v-if="clientSettings.totalGB > 0" :color="clientStats ? statsColor(clientStats) : 'default'">{{