[fix](trx-frontend-http): move band plan strip above waterfall instead of between waveform and waterfall

Relocate the band plan strip from the top of the spectrum canvas to the
bottom, directly above the waterfall canvas. Move the DOM element inside
.spectrum-wrap before the waterfall canvas so it flows naturally in the
correct position. Remove the reparenting logic since the element is now
always inside .spectrum-wrap.

https://claude.ai/code/session_01FUD2eKgeXMFGhhYTzmA4Z6
Signed-off-by: Claude <noreply@anthropic.com>

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

@@ -117,7 +117,6 @@
         <div id="hf-aprs-bar-overlay" aria-live="polite" aria-label="Recent HF APRS frames"></div>
         <div id="cw-bar-overlay" aria-live="polite" aria-label="Recent CW decodes"></div>
       </div>
-      <div id="spectrum-bandplan-strip" aria-label="Band plan allocations"></div>
       <div id="spectrum-panel" style="display:none;">
         <div class="spectrum-wrap">
           <div id="spectrum-bookmark-axis"></div>
@@ -128,6 +127,7 @@
           <div id="spectrum-db-axis" aria-hidden="true"></div>
           <div id="spectrum-bookmark-side-right" class="spectrum-bookmark-side spectrum-bookmark-side-right" aria-hidden="true"></div>
           <div id="spectrum-tooltip"></div>
+          <div id="spectrum-bandplan-strip" aria-label="Band plan allocations"></div>
           <canvas id="spectrum-waterfall-canvas" style="display:none;"></canvas>
           <div id="spectrum-freq-axis">
             <button id="spectrum-center-left-btn" class="spectrum-edge-shift spectrum-edge-shift-left" type="button" aria-label="Shift spectrum center left">&lsaquo;</button>