[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-server/trx-backend/trx-backend-soapysdr/src/dsp.rs

@@ -418,9 +418,25 @@ impl ChannelDsp {
 
     pub fn set_mode(&mut self, mode: &RigMode) {
         self.mode = mode.clone();
+        self.audio_bandwidth_hz = default_bandwidth_for_mode(mode);
         self.demodulator = Demodulator::for_mode(mode);
         self.rebuild_filters();
     }
+}
+
+/// Returns the appropriate channel filter bandwidth for a given mode.
+fn default_bandwidth_for_mode(mode: &RigMode) -> u32 {
+    match mode {
+        RigMode::LSB | RigMode::USB | RigMode::PKT | RigMode::DIG => 3_000,
+        RigMode::CW | RigMode::CWR => 500,
+        RigMode::AM => 6_000,
+        RigMode::FM => 12_500,
+        RigMode::WFM => 180_000,
+        RigMode::Other(_) => 3_000,
+    }
+}
+
+impl ChannelDsp {
 
     /// Rebuild the FIR low-pass filters with new bandwidth and tap count.
     ///