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.

scripts/remove-sharing.sql

@@ -0,0 +1,12 @@
+-- 一次性部署清理：先停止旧服务，并保留数据库与镜像配套的回滚备份。
+-- 不由应用启动流程执行；原始笔记和图片不在此脚本的清理范围内。
+BEGIN IMMEDIATE;
+DROP TABLE IF EXISTS share_items;
+DROP TABLE IF EXISTS shares;
+DELETE FROM settings WHERE key = 'share.secret';
+UPDATE settings
+SET value = json_remove(value, '$.shortcuts."note.share"', '$.shortcuts."app.shares"')
+WHERE key = 'app.settings'
+  AND (json_type(value, '$.shortcuts."note.share"') IS NOT NULL
+    OR json_type(value, '$.shortcuts."app.shares"') IS NOT NULL);
+COMMIT;