dsh-vault v0.8.9 — Round 29

✨ New features

vault_rotation soonWindowDays: tune how many days ahead counts as "expiring soon" (1–90, default 7) — tool and gateway.
vault_merge keepSource: keep the source entry after merging (default deletes it, Bitwarden-style).
vault_quick_add tags/notes: fast capture now accepts searchable tags and free-form notes.
UI: "Backup now" button — one-click encrypted backup from Settings (uses the retention policy, refreshes the backup-age badge, reports kept/pruned).

expiresAt: 0 now genuinely clears the expiry (consistent with rotationDays: 0): the store deletes the field instead of storing a zero that would report the entry as expired forever. vault_expiry now passes 0 directly instead of an internal empty-string hack.

161 tests passing (4 new: expiry-clear + soon-window, merge keepSource, quick-add tags/notes, expiry-clear via tool).

vault_rotation soonWindowDays：调整“即将到期”的天数窗口（1–90，默认 7）——工具与 gateway 均支持。
vault_merge keepSource：合并后保留源条目（默认删除，Bitwarden 风格）。
vault_quick_add tags/notes：快速录入现支持可搜索的 tags 与自由 notes。
UI：“立即备份”按钮 —— 设置页一键加密备份（遵循保留策略，刷新备份天数徽章，报告 kept/pruned）。

expiresAt: 0 现在真正清除过期（与 rotationDays: 0 一致）：store 删除该字段，而非存储 0 导致条目永远显示已过期。vault_expiry 直接传 0，移除了内部空字符串 hack。

161 个测试全部通过（新增 4 个：过期清除 + soon 窗口、merge keepSource、quick-add tags/notes、工具层过期清除）。