修复 Discord 通知因长消息导致的 400 错误

- 添加自定义消息模板，限制消息长度为 200 字符
- 简化通知格式，只保留关键信息
- 避免因过长的 commit message 导致 webhook 请求失败

.drone.yml

@@ -29,5 +29,18 @@ steps:
         from_secret: discord_webhook_id
       webhook_token:
         from_secret: discord_webhook_token
+      username: Drone CI
+      avatar_url: https://github.com/drone.png
+      message: |
+        {{#success build.status}}
+        ✅ **Build #{{build.number}}** succeeded
+        {{else}}
+        ❌ **Build #{{build.number}}** failed
+        {{/success}}
+        **Repo:** {{repo.name}}
+        **Branch:** {{build.branch}}
+        **Commit:** `{{truncate build.commit 8}}`
+        **Author:** {{build.author}}
+        **Message:** {{truncate build.message 200}}
     when:
       status: [success, failure]