feat: 实现动态插件系统 (6阶段完成)

- 阶段1: 消息类型序列化 (Serialize/Deserialize, &'static str → String)
- 阶段2: FFI 边界类型 + Plugin SDK (plugin_abi, showen-plugin-sdk crate)
- 阶段3: PluginLoader + DynamicPlugin (libloading 动态加载 .so)
- 阶段4: 版本管理 + 错误策略 (VersionManager, PluginState, 自动回退)
- 阶段5: 远程仓库客户端 (HTTP 下载 + tar.gz 安装)
- 阶段6: 示例插件 + HTTP 管理 API + 全目录 README 文档

54/54 测试通过，0 warnings。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/plugins/wifi/mod.rs

@@ -59,7 +59,7 @@ impl WifiPlugin {
             .context("wifi plugin context is not initialized")?;
 
         ctx.tx.send(Envelope {
-            from: "wifi",
+            from: "wifi".to_string(),
             to: Destination::Broadcast,
             message: Message::WifiResult(payload),
         })?;
@@ -237,20 +237,20 @@ impl Default for WifiPlugin {
 }
 
 impl Plugin for WifiPlugin {
-    fn id(&self) -> &'static str {
+    fn id(&self) -> &str {
         "wifi"
     }
 
     fn info(&self) -> PluginInfo {
         PluginInfo {
-            name: "WiFi Manager",
-            version: "0.2.0",
-            description: "WiFi 管理 (nmcli)",
+            name: "WiFi Manager".to_string(),
+            version: "0.2.0".to_string(),
+            description: "WiFi 管理 (nmcli)".to_string(),
             platform: Platform::Linux,
         }
     }
 
-    fn dependencies(&self) -> Vec<&'static str> {
+    fn dependencies(&self) -> Vec<String> {
         vec![]
     }