feat: ✨ implement geo-filtering with whitelist and blacklist support

- Added support for geo-filtering in the proxy pool, allowing configuration of allowed and blocked countries via environment variables.
- Updated `.env.example` and `docker-compose.yml` to include `ALLOWED_COUNTRIES` for whitelist functionality.
- Enhanced `CLAUDE.md`, `GEO_FILTER.md`, and `README.md` to document the new geo-filtering features and usage instructions.
- Modified proxy validation logic to prioritize whitelist over blacklist during admission checks.
- Improved WebUI to allow dynamic configuration of geo-filter settings.

.env.example

@@ -14,6 +14,11 @@ SOCKS5_STABLE_PORT=7780    # SOCKS5 最低延迟代理端口
 # 默认屏蔽中国大陆（CN），香港（HK）、澳门（MO）、台湾（TW）不受影响
 BLOCKED_COUNTRIES=CN
 
+# 允许的国家代码白名单（逗号分隔，如 US,JP,KR,SG）
+# 非空时优先于黑名单（BLOCKED_COUNTRIES 被忽略）
+# 留空 = 使用黑名单模式
+ALLOWED_COUNTRIES=
+
 # 代理服务认证配置
 # ⚠️ 代理端口默认对外开放，强烈建议启用认证！
 # 使用方式：curl -x http://username:password@host:port https://example.com