feat(cluster): LoTW badge and filter, spotter-continent filter

The L badge is a single letter, not a word: the call column is 120 px and holds
a callsign. It keeps the muted blue of a confirmation and never a status colour,
because whether a station uploads to LoTW says nothing about whether the spot is
worth chasing - those are different questions and must not share a palette.

The spotter's continent is not the DX's. It asks whether anyone near you is
hearing the band at all, which is why it earns its own control rather than
reusing the existing Continent column. The spotter callsign now travels with the
status query so the backend can resolve it against the one DXCC prefix table,
instead of a second continent rule appearing in the frontend.

Both AND with the status chips rather than joining their OR: "a new band, and
from Europe" is the question being asked. An unresolved spot is never dropped by
them - the status arrives a moment after the row, and filtering meanwhile made
the list flicker.

New counties only is the SAME state as the NEW COUNTY chip, reached a second
way, not a second filter. County chasing is a mode you switch into, and hunting
for one chip among eight is not how you switch into it.

changelog.json

@@ -2,8 +2,12 @@
   {
     "version": "0.24.4",
     "date": "",
-    "en": [],
-    "fr": []
+    "en": [
+      "DX cluster: an L badge next to a callsign marks a station that uploads to LoTW, with a matching LoTW users only filter. A Spotter continent dropdown narrows the list by where the spot came FROM — a JA report on 20 m tells a European little about their own path. New counties only joins the filter panel as a second way to the NEW COUNTY chip. All of them apply to the band map too."
+    ],
+    "fr": [
+      "Cluster DX : un badge L à côté de l indicatif signale une station qui utilise LoTW, avec le filtre Utilisateurs LoTW seulement qui va avec. Une liste déroulante Continent du spotter restreint selon l origine du spot — un report JA sur 20 m dit peu de chose à un Européen sur son propre chemin. Nouveaux comtés seulement rejoint le panneau de filtres, en second accès à la puce NOUV CTY. Le tout s applique aussi au bandmap."
+    ]
   },
   {
     "version": "0.24.3",