[e131] Drain all queued packets per loop iteration

Previously the BSD socket path read only one UDP packet per loop()
call. With multi-universe setups (e.g. 380 RGBW LEDs across 3
universes), this caused the light to re-render the entire strip
for each universe packet separately, resulting in visible tearing
and ~3x unnecessary RMT writes.

Now both socket backends drain all available packets before returning,
so multi-universe frames are applied atomically and the light only
writes once per frame. The duplicated packet processing logic is
consolidated into a shared loop with a platform-specific read_()
helper.

Tested on ESP32-IDF with 380 SK6812 RGBW LEDs (3 universes):
- Light total CPU dropped from 5820ms to 1108ms per 60s (~5x)
- Combined e131+light dropped from 6944ms to 4811ms per 60s
- Visible tearing eliminated

esphome/components/e131/e131.cpp

@@ -70,27 +70,9 @@ void E131Component::loop() {
   E131Packet packet;
   int universe = 0;
   uint8_t buf[1460];
+  ssize_t len;
 
-#if defined(USE_SOCKET_IMPL_BSD_SOCKETS) || defined(USE_SOCKET_IMPL_LWIP_SOCKETS)
-  ssize_t len = this->socket_->read(buf, sizeof(buf));
-  if (len == -1) {
-    return;
-  }
-
-  if (!this->packet_(buf, (size_t) len, universe, packet)) {
-    ESP_LOGV(TAG, "Invalid packet received of size %d.", (int) len);
-    return;
-  }
-
-  if (!this->process_(universe, packet)) {
-    ESP_LOGV(TAG, "Ignored packet for %d universe of size %d.", universe, packet.count);
-  }
-#elif defined(USE_SOCKET_IMPL_LWIP_TCP)
-  while (auto packet_size = this->udp_.parsePacket()) {
-    auto len = this->udp_.read(buf, sizeof(buf));
-    if (len <= 0)
-      continue;
-
+  while ((len = this->read_(buf, sizeof(buf))) > 0) {
     if (!this->packet_(buf, (size_t) len, universe, packet)) {
       ESP_LOGV(TAG, "Invalid packet received of size %d.", (int) len);
       continue;
@@ -100,6 +82,15 @@ void E131Component::loop() {
       ESP_LOGV(TAG, "Ignored packet for %d universe of size %d.", universe, packet.count);
     }
   }
+}
+
+ssize_t E131Component::read_(uint8_t *buf, size_t len) {
+#if defined(USE_SOCKET_IMPL_BSD_SOCKETS) || defined(USE_SOCKET_IMPL_LWIP_SOCKETS)
+  return this->socket_->read(buf, len);
+#elif defined(USE_SOCKET_IMPL_LWIP_TCP)
+  if (!this->udp_.parsePacket())
+    return -1;
+  return this->udp_.read(buf, len);
 #endif
 }
 

esphome/components/e131/e131.h

@@ -46,6 +46,7 @@ class E131Component : public esphome::Component {
   void set_method(E131ListenMethod listen_method) { this->listen_method_ = listen_method; }
 
  protected:
+  ssize_t read_(uint8_t *buf, size_t len);
   bool packet_(const uint8_t *data, size_t len, int &universe, E131Packet &packet);
   bool process_(int universe, const E131Packet &packet);
   bool join_igmp_groups_();