[fix](trx-client): reduce events source latency to <1 s

Three causes of >30 s SSE stalls:

1. SPECTRUM_IO_TIMEOUT was 300 ms — transient server jitter triggered
   false-positive spectrum failures and immediate TCP disconnects.
   Raised to 1 s to tolerate brief load spikes.

2. reconnect_delay was never reset after a successful TCP connect, so
   after a few spectrum-induced disconnects the backoff reached 10 s.
   Each new disconnect then cost 10 s of stale SSE state, and several
   cycles accumulated to >30 s.  Reset to 1 s on every successful
   TCP connect so recovery stays fast.

3. SSE pings were emitted as comments (": ping"), which EventSource
   never exposes to onmessage.  lastEventAt was therefore never updated
   by pings, causing the JS heartbeat to force-reconnect every ~20 s
   even on healthy, stable connections.  Changed to a named "ping"
   event and added es.addEventListener("ping", …) to update lastEventAt.

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/app.js

@@ -2705,6 +2705,9 @@ function connect() {
       console.error("Bad event data", e);
     }
   };
+  es.addEventListener("ping", () => {
+    lastEventAt = Date.now();
+  });
   es.onerror = () => {
     // Check if this is an auth error by looking at readyState
     if (es.readyState === EventSource.CLOSED) {