feat(chase-new): drop the frequency column, the beacons and the bands you don't have

Three cuts, all of them removing things nobody could act on.

The frequency column is gone. Clicking the row tunes the rig to it, so the
number was there to be read and never used. It is still carried on the spot —
the click is what needs it — and it is in the row's tooltip. The country takes
the space.

Modes are limited to FT8, FT4, FT2, PSK31 and RTTY. WSPR is the one worth
spelling out: it is a beacon, nobody answers a WSPR transmission, so a "new
entity on WSPR" is a path report and not a station to work — and on a quiet
band it would have been most of the list.

Bands are limited to the operator's own list. PSK Reporter carries every band
its receivers listen on, and a 13 cm decode is not an opportunity for a station
with no 13 cm.

Both tests run before the status lookup and both read a cached map: they throw
away most of the feed, so nothing downstream pays for it. The band list is
re-read when the lists are saved, so ticking a band in Settings applies to the
next decode rather than the next restart — which would have looked like the
filter not working.

app.go

@@ -656,6 +656,11 @@ type App struct {
 	// consults it once per message and must not reach the settings store.
 	chaseNew   *chaseNewStore
 	chaseNewOn atomic.Bool
+	// chaseBands is the operator's own band list, cached for the same reason:
+	// it decides whether a decode is an opportunity or a row in the way, and it
+	// is consulted once per message.
+	chaseBandsMu sync.RWMutex
+	chaseBands   map[string]bool
 	// pskr is the PSK Reporter MQTT feed, up only while the opening watch is on.
 	// It is the source that makes VHF detection work at all: the cluster and RBN
 	// carry a handful of 6 m spots where PSK Reporter carries hundreds.
@@ -13975,6 +13980,10 @@ func (a *App) SaveListsSettings(l ListsSettings) error {
 			return err
 		}
 	}
+	// The Chase New feed filters on this list per message and reads it from a
+	// cache, so a band ticked here has to reach that cache now — otherwise it
+	// takes effect at the next restart, which looks like the option not working.
+	a.refreshChaseBands()
 	return nil
 }