PC Detail: flow Details cards, drop the IP Configuration card

Details tab card layout
-----------------------
The Details tab sat on .content-grid, a two-column CSS grid. Grid packs
items into implicit rows, so every row is as tall as its tallest card and
align-items:start leaves the shorter one with dead space beneath it:
Warranty is short, Endpoint Status is tall, and Policy had to wait for the
taller of the two rather than sliding up. That read as a staggered layout.

Switched that one tab to multicol via a .details-flow modifier, which has no
rows at all - each card starts where the previous one ended, so the holes
close while cards still size to their content.

Multicol is deliberately NOT applied to .content-grid globally. The note by
that rule in style.css records why it was abandoned there: a column-span:all
child (.pap-span, used by table panels) overlaps the shorter column when the
two are unequal. That cannot happen on this tab - every panel in the details
group is a keyvalue or list render, and spansFullWidth() only returns true
for table (or a tabs panel holding one), so nothing in the subtree spans.
Monitors and Service/Process DO carry table panels and stay on grid.

The modifier is scoped to PCDetail, so the nine other detail views on
.content-grid are untouched.

Chosen over JS masonry on purpose. Masonry packs perfectly but has to
measure every card and re-measure on resize, on panel collapse and on every
async panel load - and these panels fetch after paint, so it would mean
continuous forced reflow on a page that already polls. This is pure CSS:
no measurement, no observer, no runtime cost. The tradeoff accepted is that
column bottoms can end at slightly different heights.

Cards carry break-inside: avoid so none fragments across the column break,
and the 25px spacing returns as a margin because multicol has no gap between
stacked items the way grid does.

IP Configuration card
---------------------
Removed: the data has no purpose on the page anymore. Taken out at the root
rather than hidden - the panel declaration, the /asset/<id>/ipconfig route
and the _IPCONFIG_COLUMNS constant all go, since a route with no consumer is
dead surface that still answers requests.

test_the_two_cards_do_not_duplicate_columns_beyond_the_address existed only
to police the history/config column split; with one card gone it guards
nothing, so it and its import go with it. The panel-count assertion in
test_endpoints_asset_panels_are_computer_scoped moves 15 -> 14, which is the
test doing its job and catching the removal.

IP History is unchanged and still carries the address list.

Not addressed here: three tzset() tests in test_endpoints_plugin.py fail on
Windows because time.tzset() is Unix-only. Verified pre-existing against
unmodified code; they pass in the Linux container.

frontend/src/utils/siteSettings.js

@@ -8,6 +8,14 @@ let settingsCache = null
 let inFlight = null
 let retryAfter = 0
 
+// Whether the last resolved load actually produced settings. A caller cannot
+// tell that from the value alone: a failed load and a site that simply has not
+// configured a key both read as empty, and those want opposite handling -
+// hide the feature vs try again.
+export function settingsLoadFailed() {
+  return settingsCache === null
+}
+
 // A failed load is cached briefly, not for the page session. A transient blip
 // used to blank every settings-driven link until the operator reloaded, and
 // they have no reason to know that would fix it. A short window still bounds a
@@ -151,10 +159,14 @@ export async function getServicenowUrls() {
 // setting instead of waiting for a release.
 //
 // Empty is the default and means "no link" - the id still renders as text.
+//
+// `loaded` distinguishes a real answer from a failed fetch. Both return empty
+// strings, but only one of them means "this site has no portal links".
 export async function getEntraDeviceUrls() {
   const entraUrl = await getSetting('entra_device_url', '')
   const intuneUrl = await getSetting('intune_device_url', '')
-  return { entraUrl, intuneUrl }
+  const lapsUrl = await getSetting('laps_device_url', '')
+  return { entraUrl, intuneUrl, lapsUrl, loaded: !settingsLoadFailed() }
 }
 
 // Printer hostname template. {ip} is replaced with the dash-separated IP.