feat(sessions): 一键归档 + 归档用量快照落库 — bump to v0.7.18

- archive_sessions_before：按 updatedAt 截止点批量元数据归档（1月/半月/周/指定日期）
- 归档瞬间聚合 wire.jsonl 用量按天×模型快照进 SQLite archived_sessions 表
- 统计合并：文件已删除的归档会话由快照合成 UsageRecord 注入
  get_summary/日明细，趋势/热力图/模型统计全兼容且绝不双计
- models-dev 快照同步 2026-09-14（7784 模型）；pricing 测试跟随
  deepseek-v4-flash 调价（0.15/0.60）
- cargo test 129 通过（含端到端归档→删目录→统计保留用例）、tsc 零错误

src/i18n/en.ts

@@ -225,6 +225,19 @@ export const enTranslations: Record<TranslationKey, string> = {
   roleUser: "User",
   roleAssistant: "Assistant",
   roleSystem: "System",
+  sessionsArchiveAll: "Archive old sessions",
+  archiveAllTitle: "Archive old sessions",
+  archiveAllDesc:
+    "Archives every active session whose last activity is older than the selected date. Files are kept and usage stats stay intact.",
+  archiveOptionMonth: "Older than 1 month",
+  archiveOptionHalfMonth: "Older than 15 days",
+  archiveOptionWeek: "Older than 1 week",
+  archiveOptionCustom: "Specific date",
+  archiveAllConfirm: "Archive every active session last active before {date}. Continue?",
+  archiveAllRunning: "Archiving…",
+  archiveAllDone: "Archived {archived} sessions, skipped {skipped}",
+  archiveAllFailed: "Archive failed",
+  archiveAllEmpty: "No sessions match",
 
   // Heatmap
   noData: "No data",

src/i18n/zh.ts

@@ -220,6 +220,18 @@ export const zhTranslations = {
   roleUser: "用户",
   roleAssistant: "助手",
   roleSystem: "系统",
+  sessionsArchiveAll: "一键归档",
+  archiveAllTitle: "一键归档会话",
+  archiveAllDesc: "将归档最后活跃时间早于所选日期的全部活跃会话；文件保留，统计不受影响。",
+  archiveOptionMonth: "1 个月前",
+  archiveOptionHalfMonth: "半个月前",
+  archiveOptionWeek: "1 星期前",
+  archiveOptionCustom: "指定日期",
+  archiveAllConfirm: "将归档最后活跃时间早于 {date} 的全部活跃会话。确认？",
+  archiveAllRunning: "正在归档…",
+  archiveAllDone: "已归档 {archived} 个会话，跳过 {skipped} 个",
+  archiveAllFailed: "归档失败",
+  archiveAllEmpty: "没有符合条件的会话",
 
   // Heatmap
   noData: "暂无数据",