PBUF_POOL_SIZE=4 was the minimum to pass lwIP's sanity check but caused
pbuf exhaustion during concurrent connections (API + web_server + OTA),
resulting in dropped log messages.
Set to 10 to match the BK SDK default plan and ESP8266. RTL/LN already
default to 20 and need no override.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>