[feat](trx-rs): expose WFM stereo denoise toggle

Add a server-side toggle for the multiband stereo denoiser so it can be
enabled or disabled at runtime without restarting the server.

Backend (trx-backend-soapysdr):
- Add `denoise_enabled: bool` to `WfmStereoDecoder`; gate multiband
  blend behind it (falls back to uniform single-band blend when off)
- Add `set_denoise_enabled()` method on `WfmStereoDecoder`
- Propagate `wfm_denoise: bool` through `ChannelDsp`, `SdrPipeline`,
  and `SoapySdrRig`; add `set_wfm_denoise()` at each layer
- Include `wfm_denoise` in `filter_state()` so it flows into snapshots

Protocol / core (trx-core, trx-protocol, trx-server):
- Add `SetWfmDenoise(bool)` to `RigCommand` and `ClientCommand`
- Add default `set_wfm_denoise()` trait method to `RigCat`
- Handle `SetWfmDenoise` in `rig_task.rs` and update `RigFilterState`
- Add `wfm_denoise: bool` (default `true`) to `RigFilterState`

Frontend (trx-frontend-http):
- Add `POST /toggle_wfm_denoise` endpoint
- Add "Denoise On/Off" button next to the stereo/mono audio picker
- Sync button state from SSE filter snapshot (`update.filter.wfm_denoise`)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

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

@@ -1252,6 +1252,12 @@ function render(update) {
     if (wfmDeemphasisEl && typeof update.filter.wfm_deemphasis_us === "number") {
       wfmDeemphasisEl.value = String(update.filter.wfm_deemphasis_us);
     }
+    if (wfmDenoiseBtn && typeof update.filter.wfm_denoise === "boolean") {
+      const on = update.filter.wfm_denoise;
+      wfmDenoiseBtn.textContent = on ? "On" : "Off";
+      wfmDenoiseBtn.style.borderColor = on ? "" : "var(--accent-warn, #f0a500)";
+      wfmDenoiseBtn.style.color = on ? "" : "var(--accent-warn, #f0a500)";
+    }
   }
   if (update.status && update.status.freq && typeof update.status.freq.hz === "number") {
     applyLocalTunedFrequency(update.status.freq.hz, true);
@@ -2546,6 +2552,7 @@ const audioRow = document.getElementById("audio-row");
 const wfmControlsCol = document.getElementById("wfm-controls-col");
 const wfmDeemphasisEl = document.getElementById("wfm-deemphasis");
 const wfmAudioModeEl = document.getElementById("wfm-audio-mode");
+const wfmDenoiseBtn = document.getElementById("wfm-denoise-btn");
 
 // Hide audio row if audio is not configured on the server
 fetch("/audio", { method: "GET" }).then((r) => {
@@ -2587,6 +2594,11 @@ if (wfmDeemphasisEl) {
     postPath(`/set_wfm_deemphasis?us=${encodeURIComponent(wfmDeemphasisEl.value)}`).catch(() => {});
   });
 }
+if (wfmDenoiseBtn) {
+  wfmDenoiseBtn.addEventListener("click", () => {
+    postPath("/toggle_wfm_denoise").catch(() => {});
+  });
+}
 
 function updateWfmControls() {
   if (!wfmControlsCol) return;