[fix](trx-frontend-http): move passband overlay to resolved DIG sideband

The spectrum passband overlay is drawn one-sided per mode, but DIG was
hardcoded to upper sideband — so switching the DIG sideband (or tuning
DIG/Auto across 10 MHz) left the overlay on the wrong side of the carrier
even though the backend had flipped the demodulator.

Resolve the DIG overlay direction from the current sideband policy and dial
frequency, mirroring the backend: usb → upper, lsb → lower, auto → upper at
or above 10 MHz and lower below. The overlay repaints immediately on a
policy change (optimistically on the selector, and on confirmed filter
state) and tracks frequency as it already did. Non-SDR backends keep the
historical upper-sideband overlay.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UiK871ht2uPFBHtMbxy3wD
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/generated/app.js

@@ -3729,10 +3729,19 @@ function visibleBandwidthSpecs(freqHz = lastFreqHz, mode = modeEl ? modeEl.value
   }
   return [{ centerHz: freqHz, widthHz: currentBandwidthHz }];
 }
+function digSidebandDirection() {
+  if (sdrDigSidebandPolicy === "usb") return 1;
+  if (sdrDigSidebandPolicy === "lsb") return -1;
+  if (typeof lastFreqHz === "number" && isFiniteNumber(lastFreqHz)) {
+    return lastFreqHz >= DIG_AUTO_SIDEBAND_THRESHOLD_HZ ? 1 : -1;
+  }
+  return 1;
+}
 function sidebandDirectionForMode(mode = modeEl ? modeEl.value : "") {
   const modeUpper = String(mode || "").toUpperCase();
   if (modeUpper === "LSB" || modeUpper === "CWR") return -1;
-  if (modeUpper === "USB" || modeUpper === "CW" || modeUpper === "DIG") return 1;
+  if (modeUpper === "DIG") return sdrDigSidebandSupported ? digSidebandDirection() : 1;
+  if (modeUpper === "USB" || modeUpper === "CW") return 1;
   return 0;
 }
 function displaySpanForBandwidthSpec(spec, mode = modeEl ? modeEl.value : "") {
@@ -4760,10 +4769,15 @@ function render(update) {
     }
     if (typeof update.filter.sdr_dig_sideband === "string") {
       sdrDigSidebandSupported = true;
+      const prevPolicy = sdrDigSidebandPolicy;
+      sdrDigSidebandPolicy = update.filter.sdr_dig_sideband;
       if (sdrDigSidebandEl && document.activeElement !== sdrDigSidebandEl) {
         sdrDigSidebandEl.value = update.filter.sdr_dig_sideband;
       }
       updateWfmControls();
+      if (prevPolicy !== sdrDigSidebandPolicy && lastSpectrumData) {
+        scheduleSpectrumDraw();
+      }
     }
   }
   if (typeof update.show_sdr_gain_control === "boolean") {
@@ -6634,6 +6648,8 @@ var sdrNbSupported = false;
 var sdrDigSidebandWrapEl = document.getElementById("sdr-dig-sideband-wrap");
 var sdrDigSidebandEl = document.getElementById("sdr-dig-sideband");
 var sdrDigSidebandSupported = false;
+var sdrDigSidebandPolicy = "auto";
+var DIG_AUTO_SIDEBAND_THRESHOLD_HZ = 1e7;
 fetch("/audio", { method: "GET" }).then((r) => {
   if (r.status === 404) audioRow.style.display = "none";
 }).catch(() => {
@@ -7033,6 +7049,8 @@ function submitSdrDigSideband() {
   if (!sdrDigSidebandSupported || !sdrDigSidebandEl) return;
   const policy = sdrDigSidebandEl.value || "auto";
   if (policy !== "auto" && policy !== "usb" && policy !== "lsb") return;
+  sdrDigSidebandPolicy = policy;
+  if (lastSpectrumData) scheduleSpectrumDraw();
   postPath(`/set_sdr_dig_sideband?policy=${encodeURIComponent(policy)}`).catch(() => {
   });
 }