feat(entry): type a frequency or a band into the call field

An operator reading a cluster page sees 28500 and wants to be there. The
hands are on the callsign field; reaching for the frequency box, or the
mouse, is the part that loses the station. So the call field takes a bare
number on Enter: kHz for a frequency, or a band on its own.

Ambiguity resolves to the band on purpose -- 40 is 40 m, not 40 kHz --
because neither of those kHz values is anywhere a radio tunes, and it
reads the way an operator says it. Anything with a letter in it is a
callsign and behaves exactly as before; a number that is neither a band
nor a plausible frequency does nothing at all.

Bands go through the ordinary band change, so the antennas, the per-band
power table and the outbound integrations hear about it as they would
from the dropdown. Also adds 4 m to the QSY table, so a band that can now
be typed is a band that has a frequency to go to.

frontend/src/App.tsx

@@ -292,6 +292,37 @@ function shortCatError(err?: string): string {
 }
 // bandForMHz maps a dial frequency (MHz) to its ADIF band, or '' if outside
 // every known allocation (used to auto-fill the band when the freq changes).
+// A number typed into the CALLSIGN field is a QSY, not a callsign.
+//
+// It is where the hands already are: an operator watching a cluster or a
+// spotting page reads "28500" and wants to be there, and reaching for the
+// frequency box — or worse, the mouse — is the part that loses the station. So
+// the call field takes it, on Enter, and nothing else in the entry form changes.
+//
+// Two forms, and the AMBIGUOUS ones resolve to the band deliberately. "160" is
+// the 160 m band, not 160 kHz; "40" is 40 m, not 40 kHz. Neither number is a
+// frequency anyone tunes to, so reading them as bands costs nothing and reads
+// the way an operator says it out loud.
+const ENTRY_BAND_WORDS: Record<string, string> = {
+  '2200': '2200m', '630': '630m', '160': '160m', '80': '80m', '60': '60m',
+  '40': '40m', '30': '30m', '20': '20m', '17': '17m', '15': '15m', '12': '12m',
+  '10': '10m', '6': '6m', '4': '4m', '2': '2m', '70': '70cm',
+};
+
+// entryQSYCommand reads what was typed. Returns null for anything that is not
+// unambiguously one of the two — a callsign must never be mistaken for a QSY.
+function entryQSYCommand(text: string): { band?: string; hz?: number } | null {
+  const v = text.trim();
+  if (!/^\d{1,7}$/.test(v)) return null; // digits only: a callsign has letters
+  const band = ENTRY_BAND_WORDS[v];
+  if (band) return { band };
+  const khz = Number(v);
+  // 1500 kHz to 1.3 GHz: below that is not a band anyone works, above it is a
+  // typo. A bare "500" is neither a band nor a frequency, so nothing happens.
+  if (khz >= 1500 && khz <= 1_300_000) return { hz: Math.round(khz * 1000) };
+  return null;
+}
+
 function bandForMHz(mhz: number): string {
   if (!mhz || isNaN(mhz)) return '';
   const plan: [number, number, string][] = [
@@ -702,6 +733,7 @@ export default function App() {
     '15m':  { SSB: 21300000, CW: 21030000, FT8: 21074000, FT4: 21140000, RTTY: 21080000, default: 21300000 },
     '12m':  { SSB: 24950000, CW: 24910000, FT8: 24915000, FT4: 24919000, RTTY: 24920000, default: 24950000 },
     '10m':  { SSB: 28500000, CW: 28030000, FT8: 28074000, FT4: 28180000, RTTY: 28080000, default: 28500000 },
+    '4m':   { SSB: 70200000, CW: 70100000, FT8: 70154000,                               default: 70200000 },
     '6m':   { SSB: 50150000, CW: 50080000, FT8: 50313000, FT4: 50318000,                default: 50150000 },
     '2m':   { SSB: 144300000, CW: 144050000, FT8: 144174000,                            default: 144300000 },
     '70cm': { SSB: 432300000, CW: 432050000, FT8: 432174000,                            default: 432300000 },
@@ -5469,6 +5501,25 @@ export default function App() {
     noteManualEdit();
     SetCATFrequency(Math.round(mhz * 1_000_000)).catch(() => {});
   };
+  // Carry out what was typed in the call field. Bands go through the ordinary
+  // band change, so the antennas, the power table and the outbound integrations
+  // all hear about it exactly as they would from the dropdown.
+  const applyEntryQSY = (q: { band?: string; hz?: number }) => {
+    if (q.band) {
+      onBandUserChange(q.band);
+      showToast(q.band);
+      return;
+    }
+    const hz = q.hz ?? 0;
+    if (hz <= 0) return;
+    noteManualEdit();
+    setFreqMhz((hz / 1_000_000).toFixed(6));
+    const b = bandForMHz(hz / 1_000_000);
+    if (b) setBand(b);
+    if (catState.enabled && catState.connected) SetCATFrequency(hz).catch(() => {});
+    showToast((hz / 1_000_000).toFixed(3) + ' MHz');
+  };
+
   // Mouse-wheel over a kHz digit of the top frequency readout: step the frequency
   // and (if CAT is connected) QSY the rig. The display updates optimistically on
   // every notch; the actual radio tune is debounced so a fast scroll doesn't flood
@@ -6835,6 +6886,16 @@ export default function App() {
         onKeyDown={(e) => {
           if (e.key === 'Enter' && (e.target as HTMLElement).tagName === 'INPUT') {
             e.preventDefault();
+            // A number in the call field is a QSY. Checked BEFORE ESM and before
+            // logging: both would otherwise act on a "callsign" of 28500.
+            if (e.target === callsignRef.current) {
+              const q = entryQSYCommand(callsignRef.current?.value ?? '');
+              if (q) {
+                applyEntryQSY(q);
+                setCallsign(''); // the field goes back to what it is for
+                return;
+              }
+            }
             // ESM (Enter Sends Message): fire the stage-appropriate CW macro instead
             // of logging. Falls through to the normal log when ESM isn't active.
             if (esmHandleEnter(e.target as HTMLElement)) return;