[core] Extend fast select optimization to LibreTiny platforms

Extend the ESP32 lwip_select() replacement (direct rcvevent reads +
FreeRTOS task notifications) to all LibreTiny platforms (bk72xx,
rtl87xx, ln882h).

All LibreTiny platforms have LwIP >= 2.1.3 with
lwip_socket_dbg_get_socket() and FreeRTOS task notifications. The
thread safety argument is actually stronger on LibreTiny since all
platforms are single-core ARM Cortex-M, eliminating cross-core
memory ordering concerns entirely.

Introduces USE_LWIP_FAST_SELECT feature define (set from Python
codegen for ESP32 and LibreTiny) replacing per-platform USE_ESP32
guards. The only platform-specific difference is FreeRTOS header
paths (freertos/FreeRTOS.h on ESP-IDF vs FreeRTOS.h on LibreTiny).

Expected impact on LibreTiny (same as ESP32):
- ~17x faster socket polling (direct rcvevent vs lwip_select)
- ~3.5 KB flash savings (dead code elimination of lwip_select)
- ~56 bytes static RAM savings (fd_set members excluded)
- ~200-300 bytes heap savings (UDP wake socket eliminated)

tests/components/socket/test_wake_loop_threadsafe.py

@@ -2,8 +2,11 @@ from esphome.components import socket
 from esphome.const import (
     KEY_CORE,
     KEY_TARGET_PLATFORM,
+    PLATFORM_BK72XX,
     PLATFORM_ESP32,
     PLATFORM_ESP8266,
+    PLATFORM_LN882X,
+    PLATFORM_RTL87XX,
 )
 from esphome.core import CORE
 
@@ -114,3 +117,48 @@ def test_require_wake_loop_threadsafe__non_esp32_consumes_udp_socket() -> None:
     # Verify UDP socket was consumed
     udp_consumers = CORE.data.get(socket.KEY_SOCKET_CONSUMERS_UDP, {})
     assert udp_consumers.get("socket.wake_loop_threadsafe") == 1
+
+
+def test_require_wake_loop_threadsafe__bk72xx_no_udp_socket() -> None:
+    """Test that BK72xx (LibreTiny) uses task notifications instead of UDP socket."""
+    _setup_platform(PLATFORM_BK72XX)
+    CORE.config = {"wifi": True}
+    socket.require_wake_loop_threadsafe()
+
+    # Verify the define was added
+    assert CORE.data[socket.KEY_WAKE_LOOP_THREADSAFE_REQUIRED] is True
+    assert any(d.name == "USE_WAKE_LOOP_THREADSAFE" for d in CORE.defines)
+
+    # Verify no UDP socket was consumed (LibreTiny uses FreeRTOS task notifications)
+    udp_consumers = CORE.data.get(socket.KEY_SOCKET_CONSUMERS_UDP, {})
+    assert "socket.wake_loop_threadsafe" not in udp_consumers
+
+
+def test_require_wake_loop_threadsafe__rtl87xx_no_udp_socket() -> None:
+    """Test that RTL87xx (LibreTiny) uses task notifications instead of UDP socket."""
+    _setup_platform(PLATFORM_RTL87XX)
+    CORE.config = {"wifi": True}
+    socket.require_wake_loop_threadsafe()
+
+    # Verify the define was added
+    assert CORE.data[socket.KEY_WAKE_LOOP_THREADSAFE_REQUIRED] is True
+    assert any(d.name == "USE_WAKE_LOOP_THREADSAFE" for d in CORE.defines)
+
+    # Verify no UDP socket was consumed (LibreTiny uses FreeRTOS task notifications)
+    udp_consumers = CORE.data.get(socket.KEY_SOCKET_CONSUMERS_UDP, {})
+    assert "socket.wake_loop_threadsafe" not in udp_consumers
+
+
+def test_require_wake_loop_threadsafe__ln882x_no_udp_socket() -> None:
+    """Test that LN882H (LibreTiny) uses task notifications instead of UDP socket."""
+    _setup_platform(PLATFORM_LN882X)
+    CORE.config = {"wifi": True}
+    socket.require_wake_loop_threadsafe()
+
+    # Verify the define was added
+    assert CORE.data[socket.KEY_WAKE_LOOP_THREADSAFE_REQUIRED] is True
+    assert any(d.name == "USE_WAKE_LOOP_THREADSAFE" for d in CORE.defines)
+
+    # Verify no UDP socket was consumed (LibreTiny uses FreeRTOS task notifications)
+    udp_consumers = CORE.data.get(socket.KEY_SOCKET_CONSUMERS_UDP, {})
+    assert "socket.wake_loop_threadsafe" not in udp_consumers