🔧 chore(github): standardize issue template configuration and workflow

- fix case sensitivity in issue template assignees field (Assignees → assignees)
- add silent flag to GitHub API calls in renovate workflow to reduce output noise

.github/ISSUE_TEMPLATE/1-Update-Needed.yml

@@ -3,7 +3,7 @@ description: "当前应用商店中的应用有新版本，才可填此表单。
 title: "[需要更新应用] 哪个应用需要更新？ / Which app needs an update?"
 labels:
   - Update
-Assignees: 
+assignees: 
   - pooneyy
 body:
   - type: markdown

.github/ISSUE_TEMPLATE/2-Add-New-App.yml

@@ -3,7 +3,7 @@ description: "有当前应用商店未收录的应用，请提交此表单。 /
 title: "[需要增加应用] 需要增加哪个应用？ / Which app needs to be added?"
 labels:
   - Add
-Assignees: 
+assignees: 
   - pooneyy
 body:
   - type: markdown

.github/ISSUE_TEMPLATE/3-Feedback.yml

@@ -3,7 +3,7 @@ description: "提交使用中的相关问题 / Submit issues you encounter while
 title: "[反馈问题] 哪个应用出现了问题？ / Which app has any problem?"
 labels:
   - Feedback
-Assignees: 
+assignees: 
   - pooneyy
 body:
   - type: markdown