[feat](trx-frontend-http): extract APRS to separate file and add CW decoder plugin

Extract the APRS decoder from app.js into its own aprs.js file and add
a new CW (Morse code) decoder plugin in cw.js. The CW decoder uses a
Goertzel tone detector with configurable WPM, tone frequency, and
signal threshold. The Plugins tab now has three sub-tabs: Overview,
APRS, and CW.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Stanislaw Grams <stanislawgrams@gmail.com>

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

@@ -121,6 +121,7 @@
       <div class="sub-tab-bar">
         <button class="sub-tab active" data-subtab="overview">Overview</button>
         <button class="sub-tab" data-subtab="aprs">APRS</button>
+        <button class="sub-tab" data-subtab="cw">CW</button>
       </div>
       <div id="subtab-overview" class="sub-tab-panel">
         <div class="plugin-item">
@@ -129,6 +130,12 @@
             Decodes APRS packets from RX audio using Bell 202 AFSK (1200 baud).
           </div>
         </div>
+        <div class="plugin-item">
+          <strong>CW Decoder</strong>
+          <div style="color:var(--text-muted); font-size:0.85rem; margin-top:0.2rem;">
+            Decodes CW (Morse code) from RX audio.
+          </div>
+        </div>
       </div>
       <div id="subtab-aprs" class="sub-tab-panel" style="display:none;">
         <div class="aprs-controls">
@@ -137,6 +144,19 @@
         </div>
         <div id="aprs-packets"></div>
       </div>
+      <div id="subtab-cw" class="sub-tab-panel" style="display:none;">
+        <div class="cw-controls">
+          <button id="cw-toggle-btn" type="button">Start CW</button>
+          <small id="cw-status" style="color:var(--text-muted);">Stopped</small>
+          <div id="cw-signal-indicator" class="cw-signal-off"></div>
+        </div>
+        <div class="cw-config">
+          <label>WPM <input type="number" id="cw-wpm" min="5" max="40" value="15" /></label>
+          <label>Tone (Hz) <input type="number" id="cw-tone" min="300" max="1200" value="700" /></label>
+          <label>Threshold <input type="range" id="cw-threshold" min="1" max="50" value="5" /><small id="cw-threshold-val">0.05</small></label>
+        </div>
+        <div id="cw-output"></div>
+      </div>
     </div>
     <div id="tab-about" class="tab-panel" style="display:none;">
       <table class="about-table">
@@ -157,5 +177,7 @@
     </div>
   </div>
   <script src="/app.js"></script>
+  <script src="/aprs.js"></script>
+  <script src="/cw.js"></script>
 </body>
 </html>