fix(cluster): slot colour apart from POTA, chips match badges, NEW CALL filter works

Three from review. Aqua for NEW SLOT sat right next to the POTA green — it is
now the sky cyan the panadapter palette has shipped for new-slot all along.
The NEW COUNTY chip was green while its badge is violet, and NEW SLOT's chip
was still caution yellow: chips now carry the badge's own colour (color-mix for
the muted border/背景), because a filter that does not look like what it selects
has to be learned twice.

And the NEW CALL chip matched only the DISPLAYED status, which is manufactured
by the slot-highlight option — with that option off the chip matched nothing
and read as broken. It now filters on the fact itself (worked_slot false), so
it works either way.

frontend/src/components/ClusterGrid.tsx

@@ -150,9 +150,10 @@ function statusFor(p: any): SpotStatusEntry | undefined {
 const NEW = 'var(--warning)'; // yellow: something here is new
 // NEW SLOT gets its own hue. It shared the amber NEW family while the NEW PFX
 // marker sits in caution yellow — two different facts, two near-identical
-// colours in the same cell. Aqua matches the cyan the panadapter palette
-// already gives new-slot, so the two views tell the story in the same colour.
-const NEWSLOT = 'var(--chart-2)';
+// colours in the same cell. Sky cyan, the exact colour the panadapter palette
+// ships for new-slot (#5AC8FA), so the two views tell one story — and clearly
+// apart from the POTA green the first attempt (aqua) sat next to.
+const NEWSLOT = '#5AC8FA';
 const WKD = 'var(--info)';    // blue: this callsign is already in the log
 
 // FILLING the cell that carries the fact, rather than only tinting its text.