[fix](trx-frontend-http): fix waterfall freeze, RDS bandwidth, add jog multiplier

Fix waterfall overview freezing at steady state by tracking a monotonic
push counter instead of row array length — the array size stays constant
once the waterfall is full, so the previous row-count comparison never
triggered the incremental draw path.

Fix WFM RDS not decoding when switching to WFM from a narrowband mode:
set_mode now resets audio_bandwidth_hz to the mode-appropriate default
(180 kHz for WFM) before rebuilding the FIR, preventing the 57 kHz RDS
subcarrier from being filtered out.

Add 1×/10×/100× multiplier button group next to the jog unit selector.
jogUnit × jogMult gives the effective jog step; both are persisted to
localStorage independently.

Co-Authored-By: Claude Sonnet 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

@@ -120,6 +120,14 @@
             </div>
             <div class="label"><span>Unit</span></div>
           </div>
+          <div class="freq-field mult-col">
+            <div class="jog-mult" id="jog-mult">
+              <button type="button" data-mult="1" class="active">1×</button>
+              <button type="button" data-mult="10">10×</button>
+              <button type="button" data-mult="100">100×</button>
+            </div>
+            <div class="label"><span>Mult</span></div>
+          </div>
         </div>
       </div>
       <div class="full-row controls-tray-shell">