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.

frontend/src/lib/i18n.tsx

@@ -266,7 +266,7 @@ const en: Dict = {
   'clu.selfSpot': 'Self-spot while I log', 'clu.selfSpotEvery': 'at most every', 'clu.selfSpotMinutes': 'min',
   'clu.selfSpotHint': 'Announces YOU on the master cluster when you log a QSO — the spot carries your station callsign and the frequency you just worked on, so callers find you without waiting for someone else to spot you. Sent on the first QSO of a frequency, then no more often than the gap below. Five minutes is the floor: a self-spot is traffic every user of the node sees.',
   'clu.freeNodes': 'Free public nodes:',
-  'clu.muteWorkedShort': 'No colour on worked', 'clu.slotHighlightShort': 'Colour unworked here', 'clu.muteWorked': 'No colour or badge on stations already worked',
+  'clu.lotwOnly': 'LoTW users only', 'clu.newCountyOnly': 'New counties only', 'clu.spotterCont': 'Spotter continent', 'clu.allContinents': 'All continents', 'clu.lotwBadge': 'Uploads to LoTW', 'clu.muteWorkedShort': 'No colour on worked', 'clu.slotHighlightShort': 'Colour unworked here', 'clu.muteWorked': 'No colour or badge on stations already worked',
   'clu.muteWorkedHint': '(they stay in the list, just quiet — leaves the colour for what is left to do)',
   'clu.slotHighlight': 'Colour the stations not worked on this band and mode',
   'clu.slotHighlightHint': '(by callsign, whatever the entity status says)',
@@ -686,7 +686,7 @@ const fr: Dict = {
   'clu.selfSpot': "M'auto-spotter quand j'enregistre", 'clu.selfSpotEvery': 'au plus toutes les', 'clu.selfSpotMinutes': 'min',
   'clu.selfSpotHint': "Annonce TON indicatif sur le cluster maître quand tu enregistres un QSO — le spot porte l'indicatif de station et la fréquence que tu viens de travailler, pour qu'on te trouve sans attendre que quelqu'un te spotte. Envoyé au premier QSO d'une fréquence, puis pas plus souvent que l'intervalle ci-dessous. Cinq minutes est le plancher : un auto-spot est du trafic que voient tous les utilisateurs du nœud.",
   'clu.freeNodes': 'Nœuds publics gratuits :',
-  'clu.muteWorkedShort': 'Pas de couleur sur les faits', 'clu.slotHighlightShort': 'Colorer les non faits ici', 'clu.muteWorked': 'Aucune couleur ni badge sur les stations déjà contactées',
+  'clu.lotwOnly': 'Utilisateurs LoTW seulement', 'clu.newCountyOnly': 'Nouveaux comtés seulement', 'clu.spotterCont': 'Continent du spotter', 'clu.allContinents': 'Tous les continents', 'clu.lotwBadge': 'Utilise LoTW', 'clu.muteWorkedShort': 'Pas de couleur sur les faits', 'clu.slotHighlightShort': 'Colorer les non faits ici', 'clu.muteWorked': 'Aucune couleur ni badge sur les stations déjà contactées',
   'clu.muteWorkedHint': '(elles restent dans la liste, simplement discrètes — la couleur reste pour ce qui est à faire)',
   'clu.slotHighlight': 'Colorer les stations non contactées sur cette bande et ce mode',
   'clu.slotHighlightHint': "(par indicatif, quel que soit le statut de l'entité)",