feat(liblogc): 统一集中式日志客户端库 + 全量迁移

新增:
- liblogc/: C++ 统一日志库 (libus_logc.so)，支持 set_endpoint/set_service_name/set_level
- pymsg/pymsg/logc.py: Python 统一日志模块，基于 AsyncRpcQueue

C++ 迁移 (删除 6 份本地 LogC.hpp 副本):
- ca, gateway: <us/LogC.hpp> + set_service_name
- captcha2, confs2, smtp3: using qing::LogC + set_service_name
- core: ConfsLogC → qing::LogC (ConfsTask.cpp)
- 所有 Makefile 添加 -lus_logc

Python 迁移 (6 个 log_client.py → 4 行薄包装):
- smtp, redirect80, confs, captcha, dnfs, static
- 全部委托到 pymsg.logc.LogClient

Go (waf): 保持现状，自成体系

smtp3/src/main.cpp

@@ -59,12 +59,12 @@
 #include <sys/socket.h>
 #include <unistd.h>
 
-#include "LogC.hpp"
+#include <us/LogC.hpp>
 
 namespace json = boost::json;
 namespace po = boost::program_options;
 
-using namespace smtp3;
+using qing::LogC;
 
 // ═══════════════════════════════════════════════════════════════════════════
 // 辅助: 安全的 stoi
@@ -716,6 +716,7 @@ static SendLimiter g_limiter;
 static std::unordered_map<std::string, double> g_cooldown;
 static std::mutex g_cooldown_mtx;
 static auto& g_log = LogC::instance();
+static const auto _log_init = (LogC::instance().set_service_name("smtp3-log"), true);
 
 // ═══════════════════════════════════════════════════════════════════════════
 // 8. main() — RpcServer 启动