feat(cluster): the spot list size is a setting

The list is a ring buffer that held a thousand spots, and on a busy
evening a thousand arrive in a couple of minutes. So the buffer decided
how long a spot lived, and the spot LIFETIME setting never got the chance
to expire anything: fifteen minutes meant nothing when the oldest spot
was pushed out after two.

Now settable (Preferences → Cluster, beside the lifetime, since between
them they decide the same thing), 100 to 10 000. The ceiling is a real
limit rather than a round number: every spot is matched against the
worked index and the alert rules, and is a row the cluster grid and every
open band map re-render.

frontend/src/components/SettingsModal.tsx

@@ -58,7 +58,7 @@ import {
   GetFolderSync, SaveFolderSync, PickFolderSyncFolder, GetFolderSyncStatus, SyncFolderNow,
   GetRelayAuto, SaveRelayAuto, GetStationDevices,
   GetAwardDefs, GetTrackedAwards, SaveTrackedAwards,
-  GetBandOpenSettings, SaveBandOpenSettings, GetGridScopeSettings, SaveGridScopeSettings, GetPSKReporterStatus, GetChaseNewGrids, SetChaseNewGrids, GetChaseNew, SetChaseNew, GetGridCacheStatus, GetLinkedAmps, SetLinkedAmps, GetSpotTTLMinutes, SetSpotTTLMinutes,
+  GetBandOpenSettings, SaveBandOpenSettings, GetGridScopeSettings, SaveGridScopeSettings, GetPSKReporterStatus, GetChaseNewGrids, SetChaseNewGrids, GetChaseNew, SetChaseNew, GetGridCacheStatus, GetLinkedAmps, SetLinkedAmps, GetSpotTTLMinutes, SetSpotTTLMinutes, GetSpotMax, SetSpotMax,
 } from '../../wailsjs/go/main/App';
 import type { profile as profileModels } from '../../wailsjs/go/models';
 import type { LookupSettingsForm, StationSettingsForm, ListsSettingsForm, ModePresetForm } from '@/types';
@@ -1942,6 +1942,7 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
   const [chaseNew, setChaseNew] = useState(false);
   const [spotTTL, setSpotTTL] = useState(0);
   const [spotTTLText, setSpotTTLText] = useState('0');
+  const [spotMaxText, setSpotMaxText] = useState('1000');
   const [gridStat, setGridStat] = useState<any>(null);
   const [pskrStatus, setPskrStatus] = useState<any>(null);
   const saveBandOpen = async (next: any) => {
@@ -1955,6 +1956,7 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
       try { setChaseNew(await GetChaseNew()); } catch { /* defaults stand */ }
       try { setLinkedAmps((await GetLinkedAmps()) ?? []); } catch { /* defaults stand */ }
       try { const n = await GetSpotTTLMinutes(); setSpotTTL(n); setSpotTTLText(String(n)); } catch { /* defaults stand */ }
+      try { const n = await GetSpotMax(); setSpotMaxText(String(n)); } catch { /* defaults stand */ }
     })();
     // Poll the feed while the panel is open: a live count is the only thing that
     // distinguishes "connected" from "connected and receiving nothing".
@@ -4973,6 +4975,28 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
                 }} />
               <span className="text-xs text-muted-foreground">{t('clu.spotTtlHint')}</span>
             </div>
+            {/* The list size, beside the lifetime because between them they decide
+                the same thing: whichever runs out first removes the spot. */}
+            <div className="flex items-center gap-3 flex-wrap">
+              <span className="text-sm">{t('clu.spotMax')}</span>
+              <div className="inline-flex rounded-md border border-border overflow-hidden text-xs">
+                {[500, 1000, 2500, 5000].map((v) => (
+                  <button key={v} type="button"
+                    onClick={() => { setSpotMaxText(String(v)); SetSpotMax(v).catch(() => {}); }}
+                    className={cn('px-2.5 py-1.5 font-medium', Number(spotMaxText) === v ? 'bg-primary text-primary-foreground' : 'text-muted-foreground hover:bg-muted')}>
+                    {v}
+                  </button>
+                ))}
+              </div>
+              <Input className="h-8 w-24" value={spotMaxText}
+                onChange={(e) => {
+                  const raw = e.target.value.replace(/[^0-9]/g, '');
+                  setSpotMaxText(raw);
+                  const n = parseInt(raw, 10);
+                  if (Number.isFinite(n) && n > 0) SetSpotMax(Math.min(10000, n)).catch(() => {});
+                }} />
+              <span className="text-xs text-muted-foreground">{t('clu.spotMaxHint')}</span>
+            </div>
           </div>
 
           <div className="border-t border-border/60 pt-3 space-y-2">