Title: Implement minimal core framework with PL injection and update build config

Key features implemented:
- Updated package metadata and dependencies in PKG-INFO, setup files
- Added main.py entry point for backward compatibility with README launch method
- Enhanced CLI with config options, system info command, and proper signal handling
- Implemented minimal PluginManager loading only plugin-loader core plugin
- Refactored PluginLoader to follow minimal core design, removed sandbox/isolation complexity
- Updated auto-dependency plugin with safer PL injection mechanism and disabled pl_injection
- Removed legacy plugin files (firewall, frp_proxy, ftp_server, multi_lang_deploy, ops_toolbox, security_gateway) as functionality moved to core plugin system
- Improved gitignore with comprehensive ignore patterns

The changes implement a minimal core framework design where only the plugin-loader is directly loaded by the core, with all other plugins managed through the PL injection mechanism, significantly simplifying the architecture.

main.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+"""FutureOSS 主入口 - 兼容旧版启动方式
+
+此文件用于兼容 README 中描述的 `python main.py` 启动方式。
+推荐使用 `oss serve` 命令启动。
+"""
+import sys
+from pathlib import Path
+
+# 确保 workspace 在 Python 路径中
+workspace_dir = Path(__file__).parent.resolve()
+if str(workspace_dir) not in sys.path:
+    sys.path.insert(0, str(workspace_dir))
+
+from oss.cli import main
+
+if __name__ == "__main__":
+    main()