WebUI: per-signal vscale toolbar, active-signal highlighting, zoom fix

- Per-signal, per-plot vertical scale state (sigVScale keyed by plotId:signalKey)
  so the same signal in two plots has fully independent vscale config
- Active signal redrawn on top of all series with 2× line width for clear
  visual identification; badge click toggles selection and opens/closes the
  embedded vscale toolbar (click same badge again to deselect)
- Vscale configurator moved from floating popup to a slim toolbar strip
  anchored inside the plot card, with an × close button
- Trigger dropdown shows one entry per array signal with [0…N-1] label;
  opening it shows an index-picker dialog to choose the element
- Zoom resampling: when server returns no data for a zoomed range, fall
  back to the local circular buffer instead of returning empty arrays

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Test/MARTeApp/TestApp.cfg

@@ -3,7 +3,9 @@
  *
  * Three independent RT threads demonstrate all four UDPStreamer time modes:
  *
- * Thread1 – "Streamer" port 44500 (scalar signals, PacketTime)
+ * Thread1 – "Streamer" port 44500 TCP control / 44503 UDP multicast 239.0.0.1
+ *           (scalar signals, auto-accumulated to arrays[10], multicast mode,
+ *            100 Hz flush = 10 samples per packet, 1 kHz source)
  *   Counter  – uint32 cycle counter
  *   Time     – uint32 time in microseconds (LinuxTimer, 1 kHz)
  *   Sine1    – float32, 1 Hz, quantised to uint16 on wire  (PacketTime)
@@ -413,10 +415,18 @@ $TestApp = {
         }
 
         // ── Streamer: scalar signals, PacketTime (port 44500) ─────────────────
+        //  Multicast mode: clients connect via TCP on port 44500 to receive the
+        //  CONFIG packet, then join 239.0.0.1:44503 to receive DATA datagrams.
+        //  Auto publishing ensures data is sent every RT cycle (1 kHz = 1 ms
+        //  temporal resolution) but never faster, so the rate is bounded.
         +Streamer = {
             Class = UDPStreamer
             Port = 44500
+            MulticastGroup = "239.0.0.1"
+            DataPort = 44503
             MaxPayloadSize = 1400
+            PublishingMode = "Accumulate"
+            MinRefreshRate = 100
             Signals = {
                 Counter = {
                     Type = uint32