feat(ui): streamline workspace settings and remove sharing

Unify compact workspace controls and panel transitions, move directory actions into the context menu, and remove backlink UI.

Reorganize settings with searchable sections, per-setting resets, shortcut search, and accurate save feedback.

Remove sharing UI, APIs, authentication helpers, and storage code; provide a transactional cleanup script with retirement tests. Reject directories during orphan image cleanup and cover mixed-batch preservation.

web/src/highlight/protocol.ts

@@ -6,7 +6,7 @@ export interface HighlightRequest {
   code: string
 }
 
-// 保留 Prism 的嵌套 token 与原文，编辑器和分享页共用官方 token 类样式。
+// 保留 Prism 的嵌套 token 与原文，编辑器使用官方 token 类样式。
 export type TokenRun = (string | { classes: string; content: TokenRun })[]
 
 // 语言不受支持时 tokens 为 null；实际失败必须与纯文本结果区分。