Phase 7: scheduled (recurring) backups (0.7.0)

- BackupSchedule model + schedule_service: next-run calc (hourly/daily/weekly,
  UTC), background scheduler loop (lifespan), run-one with retention pruning
  (keep newest N per stack on the destination), backup_failed notify event.
- routers/schedules.py: schedules CRUD + run-now; registered in main.py.
- Frontend: api/schedules.ts + Settings → Scheduled backups (list with next/last
  run + status, enable/disable, run-now, delete; add form with stack/destination/
  frequency/time/weekday/retention/volumes).

Rough-verified only (per request): py_compile, frontend tsc build, app import
(95 routes), next-run math sanity. Full live run to be tested after deploy.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -5,7 +5,7 @@ as intuitive as Dockge, as capable as Portainer for Compose workflows.
 
 > **Status:** Phase 1 (Core) + Phase 2 (Volumes & GPU) + Phase 3 (Quality of
 > Life) + Phase 4 (Operations) + Phase 5 (Multi-host) + Phase 6 (Backup
-> destinations) complete.
+> destinations) + Phase 7 (Scheduled backups) complete.
 
 ## What works today (Phase 1)
 
@@ -91,6 +91,16 @@ as intuitive as Dockge, as capable as Portainer for Compose workflows.
   and restore (volumes included) directly from it. Remote backups can also be
   deleted from the UI.
 
+### Phase 7 — Scheduled backups
+
+- **Recurring backups**: schedule a stack to back up to a destination **hourly,
+  daily, or weekly** (UTC) under **Settings → Scheduled backups**. A background
+  scheduler runs due jobs every minute and records last/next run + status.
+- **Retention**: keep the newest *N* backups per stack on the destination; older
+  ones are pruned automatically.
+- **Run now** for an on-demand run, plus a `backup_failed` notification event
+  wired into the webhook system.
+
 ## Deploying an agent on another host
 
 ```bash
@@ -227,6 +237,14 @@ DELETE /api/backups/destinations/{id}/backups/{name}
 POST   /api/stacks/{id}/backup/push                POST /api/stacks/restore-from
 ```
 
+### Phase 7 endpoints
+
+```
+GET    /api/backups/schedules                     POST /api/backups/schedules
+PUT    /api/backups/schedules/{id}                 DELETE /api/backups/schedules/{id}
+POST   /api/backups/schedules/{id}/run
+```
+
 ## Security notes
 
 - The Docker socket is only ever touched by the backend process; it is never