fix(dbbackup): 备份新鲜度按最新的 daily 包算，手动或异地包不再掩盖停掉的定时任务

docs/openapi.yaml

@@ -382,9 +382,19 @@ components:
                 Why the bundle lacks the MinecraftServer objects (the cluster did not
                 answer the export), when it does. A restore from it brings back the
                 database but no servers.
+            daily_at:
+              type: string
+              format: date-time
+              description: >
+                When the newest daily bundle (felis-db-backup.timer) in dir was
+                written, as of this record; absent when dir held none. Equal to
+                at when this record is a daily one.
         stale:
           type: boolean
-          description: True when there is no record or it is older than max_age_seconds.
+          description: >
+            True when there is no record, no daily bundle, or the newest daily
+            bundle is older than max_age_seconds. A newer manual, pre-migrate or
+            off-site bundle leaves it as it is: the daily timer has still stopped.
         max_age_seconds:
           type: integer
           format: int64
@@ -3684,8 +3694,8 @@ paths:
       description: >-
         What the host's felis-db-backup.timer (or a manual `felis db backup`)
         last recorded in platform_settings. last is null before the first
-        backup; stale is true then, and whenever the newest backup is older than
-        max_age_seconds. Read-only: backups run on the host, never through the API.
+        backup; stale is true then, and whenever the newest daily backup
+        (last.daily_at) is missing or older than max_age_seconds. Read-only: backups run on the host, never through the API.
       x-felis-face: [external]
       x-felis-tier: admin
       security: [{ sessionCookie: [] }]