feat: unify proxy config and centralize runtime logging

.env.example

@@ -5,6 +5,10 @@ BINANCE_API_URL=https://api.binance.com
 SOCKS5_PROXY=socks5://127.0.0.1:7890
 USE_PROXY=true
 
+# send_msg 独立代理（可选，优先级高于 SOCKS5_PROXY）
+# SEND_MSG_PROXY=socks5://127.0.0.1:7891
+# SEND_MSG_PROXY_PORT=7891
+
 # Data Configuration
 DATA_CACHE_DIR=./data/cache
 LOOKBACK_1H=168      # 1 week for 1h data