feat: 接入 LogHive 远程日志系统

- 添加 LogHiveHandler，启动时自动挂载到 root logger
- 所有 logging 日志自动异步发送到 LogHive，不影响主业务
- vendored loghive-client 包，Docker 构建时自动安装
- API Key 缺失时自动跳过，不影响本地开发

vendor/loghive_client/__init__.py

@@ -0,0 +1,20 @@
+"""LogHive Client — Send logs from your Python projects to LogHive.
+
+Usage:
+    from loghive_client import LogHiveLogger
+
+    logger = LogHiveLogger(
+        project="my-project",
+        api_key="your-api-key",
+        endpoint="http://localhost:8000",
+    )
+
+    logger.info("User logged in", extra={"user_id": 42})
+    logger.error("Database connection failed", exc_info=True)
+"""
+
+from loghive_client.client import LogHiveLogger
+from loghive_client.async_client import AsyncLogHiveLogger
+from loghive_client.handler import LogHiveHandler
+
+__all__ = ["LogHiveLogger", "AsyncLogHiveLogger", "LogHiveHandler"]