feat: Super Check Partial + N+1 helper; fix Flex binding to SmartSDR CAT; telemetry callsign wait

- SCP/N+1: new internal/scp downloads the community MASTER.SCP master list and a
  docked two-column widget shows, as you type a call, the known calls containing it
  (Partial) and the calls one edit away (N+1) — click to fix a busted call. Opt-in
  in Settings → General; top-bar toggle; queried debounced on callsign input.
- Flex: OpsLog's GUI-client detection was too loose and could bind to "SmartSDR CAT"
  (or DAX) — both carry "smartsdr" in the program name — instead of the real GUI
  client, making SmartSDR CAT drop and reconnect in a loop while OpsLog was open.
  Now it binds only to a real SmartSDR/Maestro GUI client (e.g. a FLEX-8600M's
  integrated screen) and excludes cat/dax; dropped the risky empty-program fallback.
- Telemetry: on a fresh install the callsign isn't set at launch, so the once-a-day
  heartbeat recorded the machine UUID. Now it waits (~10 min) for the operator to
  enter their callsign before sending, falling back to the UUID only if none appears.

frontend/src/components/SettingsModal.tsx

@@ -39,6 +39,7 @@ import {
   GetPOTAToken, SavePOTAToken,
   TestLoTWUpload, ListTQSLStationLocations,
   DownloadLoTWUsers, GetLoTWUsersStatus,
+  GetScpStatus, SetScpEnabled, DownloadScp,
   DownloadULSCounties, ULSStatus, BackfillUSCounties,
   ComputeStationInfo,
   GetUIPref, SetUIPref,
@@ -1253,6 +1254,21 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
     catch (e: any) { setLotwTest({ ok: false, msg: String(e?.message ?? e) }); }
     finally { setLotwUsersBusy(false); }
   };
+  // Super Check Partial / N+1 callsign helper: enabled flag + master-list status.
+  const [scp, setScp] = useState<{ enabled: boolean; count: number; updated?: string }>({ enabled: false, count: 0 });
+  const [scpBusy, setScpBusy] = useState(false);
+  useEffect(() => { GetScpStatus().then((s) => setScp(s as any)).catch(() => {}); }, []);
+  const toggleScp = async (on: boolean) => {
+    setScp((s) => ({ ...s, enabled: on }));
+    setScpBusy(true);
+    try { await SetScpEnabled(on); const s = await GetScpStatus(); setScp(s as any); } catch {}
+    finally { setScpBusy(false); }
+  };
+  const downloadScp = async () => {
+    setScpBusy(true);
+    try { await DownloadScp(); const s = await GetScpStatus(); setScp(s as any); } catch {}
+    finally { setScpBusy(false); }
+  };
   // US Counties (offline FCC ULS) — download progress arrives via events.
   const [ulsStatus, setUlsStatus] = useState<{ count: number; updated_at?: string }>({ count: 0 });
   const [ulsBusy, setUlsBusy] = useState(false);
@@ -4761,6 +4777,28 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
             <Checkbox checked={showBeamMap} onCheckedChange={(c) => { const v = !!c; setShowBeamMap(v); writeUiPref('opslog.showBeamOnMap', v ? '1' : '0'); }} />
             {t('gen.showBeam')}
           </label>
+
+          {/* Super Check Partial / N+1 — downloads the community MASTER.SCP list and
+              shows a two-column callsign helper (partial matches + one-edit calls). */}
+          <div className="border-t border-border/60 pt-3 space-y-2">
+            <label className="flex items-center gap-2 text-sm cursor-pointer">
+              <Checkbox checked={scp.enabled} disabled={scpBusy} onCheckedChange={(c) => toggleScp(!!c)} />
+              {t('scp.enable')}
+            </label>
+            <p className="text-[11px] text-muted-foreground">{t('scp.settingsHint')}</p>
+            {scp.enabled && (
+              <div className="flex items-center gap-3">
+                <Button variant="outline" size="sm" onClick={downloadScp} disabled={scpBusy}>
+                  <ArrowDown className="size-3.5" /> {scpBusy ? t('scp.downloading') : t('scp.download')}
+                </Button>
+                <span className="text-xs text-muted-foreground">
+                  {scp.count > 0
+                    ? t('scp.loaded', { n: scp.count.toLocaleString(), date: scp.updated ? new Date(scp.updated).toLocaleDateString() : '?' })
+                    : t('scp.notLoaded')}
+                </span>
+              </div>
+            )}
+          </div>
           <label className="flex items-center gap-2 text-sm cursor-pointer">
             <Checkbox checked={startEqEnd} onCheckedChange={(c) => { const v = !!c; setStartEqEnd(v); writeUiPref('opslog.startEqualsEnd', v ? '1' : '0'); }} />
             {t('gen.startEqEnd')} <span className="text-xs text-muted-foreground">{t('gen.startEqEndHint')}</span>