[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-core/src/rig/command.rs

@@ -34,5 +34,6 @@ pub enum RigCommand {
     SetBandwidth(u32),
     SetFirTaps(u32),
     SetWfmDeemphasis(u32),
+    SetWfmDenoise(bool),
     GetSpectrum,
 }

src/trx-core/src/rig/controller/handlers.rs

@@ -517,6 +517,7 @@ pub fn command_from_rig_command(cmd: RigCommand) -> Box<dyn RigCommandHandler> {
         | RigCommand::SetBandwidth(_)
         | RigCommand::SetFirTaps(_)
         | RigCommand::SetWfmDeemphasis(_)
+        | RigCommand::SetWfmDenoise(_)
         | RigCommand::GetSpectrum => Box::new(GetSnapshotCommand),
     }
 }

src/trx-core/src/rig/mod.rs

@@ -165,6 +165,16 @@ pub trait RigCat: Rig + Send {
         )))
     }
 
+    fn set_wfm_denoise<'a>(
+        &'a mut self,
+        _enabled: bool,
+    ) -> Pin<Box<dyn Future<Output = DynResult<()>> + Send + 'a>> {
+        Box::pin(std::future::ready(Err(
+            Box::new(response::RigError::not_supported("set_wfm_denoise"))
+                as Box<dyn std::error::Error + Send + Sync>,
+        )))
+    }
+
     /// Return the current filter state if this backend supports filter controls.
     fn filter_state(&self) -> Option<state::RigFilterState> {
         None

src/trx-core/src/rig/state.rs

@@ -271,12 +271,18 @@ pub struct RigFilterState {
     pub cw_center_hz: u32,
     #[serde(default = "default_wfm_deemphasis_us")]
     pub wfm_deemphasis_us: u32,
+    #[serde(default = "default_wfm_denoise")]
+    pub wfm_denoise: bool,
 }
 
 fn default_wfm_deemphasis_us() -> u32 {
     75
 }
 
+fn default_wfm_denoise() -> bool {
+    true
+}
+
 /// Spectrum data from SDR backends (FFT magnitude over the full capture bandwidth).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct SpectrumData {