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.

store/@{FutureOSS}/plugin-loader-pro/fallback/handler.py

@@ -0,0 +1,49 @@
+"""降级处理器"""
+from typing import Callable, Any, Optional
+from ..utils.logger import ProLogger
+
+
+class FallbackStrategy:
+    """降级策略枚举"""
+    RETURN_DEFAULT = "return_default"
+    RETURN_CACHE = "return_cache"
+    RETURN_NULL = "return_null"
+    CALL_ALTERNATIVE = "call_alternative"
+
+
+class FallbackHandler:
+    """降级处理器"""
+
+    def __init__(self, strategy: str = FallbackStrategy.RETURN_NULL,
+                 default_value: Any = None,
+                 alternative_func: Callable = None):
+        self.strategy = strategy
+        self.default_value = default_value
+        self.alternative_func = alternative_func
+        self._cache = {}
+
+    def execute(self, func: Callable, plugin_name: str, *args, **kwargs) -> Any:
+        """执行降级逻辑"""
+        try:
+            result = func(*args, **kwargs)
+            self._cache[plugin_name] = result
+            return result
+        except Exception as e:
+            ProLogger.warn("fallback", f"插件 {plugin_name} 执行失败，触发降级: {e}")
+            return self._apply_fallback(plugin_name)
+
+    def _apply_fallback(self, plugin_name: str) -> Any:
+        """应用降级策略"""
+        if self.strategy == FallbackStrategy.RETURN_DEFAULT:
+            return self.default_value
+        elif self.strategy == FallbackStrategy.RETURN_CACHE:
+            return self._cache.get(plugin_name)
+        elif self.strategy == FallbackStrategy.RETURN_NULL:
+            return None
+        elif self.strategy == FallbackStrategy.CALL_ALTERNATIVE:
+            if self.alternative_func:
+                try:
+                    return self.alternative_func()
+                except Exception as e:
+                    ProLogger.error("fallback", f"备选方案也失败了: {e}")
+            return None