[style](trx-frontend): use select element for WFM denoise control

Replace the checkbox with an On/Off select dropdown to match the
styling of the other WFM controls (Deemp, Audio) in the controls row.

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

src/trx-client/trx-frontend/trx-frontend-http/assets/web/index.html

@@ -174,7 +174,10 @@
                   </label>
                   <label class="wfm-control">
                     <span class="wfm-control-label">Denoise</span>
-                    <input type="checkbox" id="wfm-denoise" checked />
+                    <select id="wfm-denoise" class="status-input">
+                      <option value="on">On</option>
+                      <option value="off">Off</option>
+                    </select>
                   </label>
                   <div class="wfm-gain-group" id="sdr-gain-controls">
                     <label class="wfm-control">