[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-protocol/src/codec.rs

@@ -298,6 +298,7 @@ mod tests {
                 fir_taps: 64,
                 cw_center_hz: 700,
                 wfm_deemphasis_us: 75,
+                wfm_denoise: true,
             }),
             ..minimal_snapshot()
         })
@@ -334,6 +335,7 @@ mod tests {
                 fir_taps: 128,
                 cw_center_hz: 700,
                 wfm_deemphasis_us: 50,
+                wfm_denoise: true,
             }),
             ..minimal_snapshot()
         };

src/trx-protocol/src/mapping.rs

@@ -51,6 +51,7 @@ pub fn client_command_to_rig(cmd: ClientCommand) -> RigCommand {
         ClientCommand::SetWfmDeemphasis { deemphasis_us } => {
             RigCommand::SetWfmDeemphasis(deemphasis_us)
         }
+        ClientCommand::SetWfmDenoise { enabled } => RigCommand::SetWfmDenoise(enabled),
         ClientCommand::GetSpectrum => RigCommand::GetSpectrum,
     }
 }
@@ -95,6 +96,7 @@ pub fn rig_command_to_client(cmd: RigCommand) -> ClientCommand {
         RigCommand::SetWfmDeemphasis(deemphasis_us) => {
             ClientCommand::SetWfmDeemphasis { deemphasis_us }
         }
+        RigCommand::SetWfmDenoise(enabled) => ClientCommand::SetWfmDenoise { enabled },
         RigCommand::GetSpectrum => ClientCommand::GetSpectrum,
     }
 }

src/trx-protocol/src/types.rs

@@ -39,6 +39,7 @@ pub enum ClientCommand {
     SetBandwidth { bandwidth_hz: u32 },
     SetFirTaps { taps: u32 },
     SetWfmDeemphasis { deemphasis_us: u32 },
+    SetWfmDenoise { enabled: bool },
     GetSpectrum,
 }