feat(settings): collapse Discord sub-options under one header

"Fetch covers from Apple Music" and "Custom text templates" are now both
tucked into a single collapsible "Advanced Discord options" block (default
collapsed) that only appears when Discord Rich Presence is enabled.
Reduces vertical noise in Settings → General for the common case where
users just flip Rich Presence on and leave the defaults.

Uses the same chevron-rotate pattern as the font picker and contributors
list. Adds `settings.discordOptions` key in all 8 locales.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/locales/zh.ts

@@ -533,6 +533,7 @@ export const zhTranslation = {
     discordRichPresenceDesc: '在 Discord 个人资料上显示当前播放的曲目。需要 Discord 处于运行状态。',
     discordAppleCovers: '通过 Apple Music 为 Discord 获取封面',
     discordAppleCoversDesc: '将艺术家和专辑名称发送至 Apple 搜索 API，以为 Discord 个人资料查找封面图片。出于隐私考虑，默认禁用。',
+    discordOptions: 'Discord 高级选项',
     discordTemplates: '自定义文本模板',
     discordTemplatesDesc: '自定义在 Discord 个人资料上显示的信息。变量：{title}, {artist}, {album}',
     discordTemplateDetails: '主行 (details)',