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/video/mod.rs

@@ -48,7 +48,7 @@ impl VideoPlugin {
         };
 
         if let Err(error) = ctx.tx.send(Envelope {
-            from: self.id(),
+            from: self.id().to_string(),
             to: Destination::Broadcast,
             message: Message::PlayerStatus(status),
         }) {
@@ -70,7 +70,7 @@ impl VideoPlugin {
         }
 
         if let Err(error) = ctx.tx.send(Envelope {
-            from: self.id(),
+            from: self.id().to_string(),
             to: Destination::Broadcast,
             message: Message::StateChanged {
                 old_state,
@@ -89,20 +89,20 @@ impl Default for VideoPlugin {
 }
 
 impl Plugin for VideoPlugin {
-    fn id(&self) -> &'static str {
+    fn id(&self) -> &str {
         "video"
     }
 
     fn info(&self) -> PluginInfo {
         PluginInfo {
-            name: "Video Player",
-            version: "0.2.0",
-            description: "视频播放引擎 (OpenCV)",
+            name: "Video Player".to_string(),
+            version: "0.2.0".to_string(),
+            description: "视频播放引擎 (OpenCV)".to_string(),
             platform: Platform::Any,
         }
     }
 
-    fn dependencies(&self) -> Vec<&'static str> {
+    fn dependencies(&self) -> Vec<String> {
         vec![]
     }
 
@@ -130,9 +130,9 @@ impl Plugin for VideoPlugin {
         self.worker = Some(handle);
 
         ctx.tx.send(Envelope {
-            from: self.id(),
+            from: self.id().to_string(),
             to: Destination::Manager,
-            message: Message::PluginReady(self.id()),
+            message: Message::PluginReady(self.id().to_string()),
         })?;
 
         self.publish_status();
@@ -150,8 +150,8 @@ impl Plugin for VideoPlugin {
                         // 恢复播放时重新获取防息屏锁
                         if let Some(ctx) = &self.ctx {
                             let _ = ctx.tx.send(Envelope {
-                                from: self.id(),
-                                to: Destination::Plugin("screen"),
+                                from: self.id().to_string(),
+                                to: Destination::Plugin("screen".to_string()),
                                 message: Message::ScreenLockRequest(true),
                             });
                         }
@@ -161,8 +161,8 @@ impl Plugin for VideoPlugin {
                         // 暂停时释放防息屏锁
                         if let Some(ctx) = &self.ctx {
                             let _ = ctx.tx.send(Envelope {
-                                from: self.id(),
-                                to: Destination::Plugin("screen"),
+                                from: self.id().to_string(),
+                                to: Destination::Plugin("screen".to_string()),
                                 message: Message::ScreenLockRequest(false),
                             });
                         }
@@ -324,7 +324,7 @@ fn publish_status_message(
     status: PlayerStatusData,
 ) -> Result<()> {
     tx.send(Envelope {
-        from: "video",
+        from: "video".to_string(),
         to: Destination::Broadcast,
         message: Message::PlayerStatus(status),
     })?;
@@ -345,7 +345,7 @@ fn publish_state_changed(
     }
 
     tx.send(Envelope {
-        from: "video",
+        from: "video".to_string(),
         to: Destination::Broadcast,
         message: Message::StateChanged {
             old_state,