fix: send socket events only from loop()

Every socket event is formatted into one static buffer by one shared
formatter.  setConnected() runs on the WiFi/Ethernet event task and sent
memStatus, wifiStrength and ethernet, then ran sockEmit.loop(), while
loop() could be building its own event.  _safecat() checks the room and
then writes at _len, so another task moving _len in between could write
past the end of g_response.

setConnected() now sends nothing.  loop() broadcasts the status every
STATUS_EMIT_MS (30 s): memStatus, then ethernet, or wifiStrength when it
moved 3 dBm or changed channel.  A client that connects still gets all
of it at once from initClients(), so needsBroadcast and the 1.5 s tick
go, and so does the 1.5 s memStatus for the config panel.

SocketEmitter records loop()'s task in begin().  Off it, beginEmit()
logs and hands out a formatter that writes nothing, and endEmit(),
endEmitRoom() and loop() do nothing.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/entryPoints/Web.cpp

@@ -327,7 +327,6 @@ void Web::handleDiscovery(AsyncWebServerRequest *request) {
   if(request->method() == HTTP_POST || request->method() == HTTP_GET) {
     ESP_LOGD(TAG, "Async Discovery Requested");
     sendSnapshot(request, snapshot_doc_t::discovery, 0, discoveryHeader);
-    net.needsBroadcast = true;
   }
   else
     request->send(500, _encoding_text, "Invalid http method");