Phase 4: backups w/ volumes, notifications, settings & users, audit page (0.4.0)

- Backup/restore: per-stack tar.gz incl. named-volume snapshots (helper
  container), upload restore with rename/overwrite/conflict detection.
- Notifications: ntfy/Discord/Slack/Gotify/generic webhooks, per-event
  subscriptions; wired into the update checker and stack lifecycle.
- Settings page: update-check interval, webhook CRUD + test, user management
  (with last-admin safeguards).
- Audit log page (searchable, paginated).
- Mobile-responsive sidebar/layout.

Multi-host agents and remote backup destinations (SFTP/S3) deferred.

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

README.md

@@ -4,7 +4,8 @@ A self-hosted Docker Compose manager for power users and homelab enthusiasts —
 as intuitive as Dockge, as capable as Portainer for Compose workflows.
 
 > **Status:** Phase 1 (Core) + Phase 2 (Volumes & GPU) + Phase 3 (Quality of
-> Life) complete. Multi-host agents, backups and notifications land in Phase 4.
+> Life) + Phase 4 (Operations) complete. Multi-host agents are planned for a
+> later phase.
 
 ## What works today (Phase 1)
 
@@ -55,6 +56,24 @@ as intuitive as Dockge, as capable as Portainer for Compose workflows.
   Paperless-NGX, Gitea) with `{{VARIABLE}}` forms; save any stack as a custom template.
 - **Healthcheck status** surfaced per container in the stack overview.
 
+### Phase 4 — Operations
+
+- **Backup & restore**: per-stack `.tar.gz` backups including named-volume contents
+  (snapshotted via a throwaway helper container); restore via upload with optional
+  rename, volume restore, and overwrite/conflict detection.
+- **Notification webhooks**: ntfy, Discord, Slack, Gotify, or generic JSON, each
+  subscribed to chosen events (image update available, stack start/stop/error,
+  pull failed). Managed in **Settings → Notifications**; env `NOTIFY_WEBHOOKS`
+  still supported for generic endpoints.
+- **Settings page**: tune the update-check interval, manage webhooks, and manage
+  users (create/disable/delete, promote/demote, with last-admin safeguards).
+- **Audit log page**: searchable, paginated view of all recorded actions.
+- **Mobile-responsive layout**: off-canvas sidebar + adaptive spacing.
+
+> **Not yet:** multi-host agents (a second deployable agent app + remote proxying)
+> and remote backup destinations (SFTP/S3) are intentionally deferred to a future
+> phase — backups currently download to / upload from the browser.
+
 ## Architecture
 
 ```
@@ -143,6 +162,18 @@ GET    /api/templates | /{id}                     POST /api/templates/{id}/insta
 POST   /api/templates                             DELETE /api/templates/custom/{slug}
 ```
 
+### Phase 4 endpoints
+
+```
+GET    /api/stacks/{id}/backup?include_volumes=&stop_first=   POST /api/stacks/restore
+GET    /api/settings                              PUT  /api/settings
+GET    /api/settings/webhooks                     POST /api/settings/webhooks
+PUT    /api/settings/webhooks/{id}                DELETE /api/settings/webhooks/{id}
+POST   /api/settings/webhooks/{id}/test
+GET    /api/auth/users                            POST /api/auth/users
+PATCH  /api/auth/users/{id}                        DELETE /api/auth/users/{id}
+```
+
 ## Security notes
 
 - The Docker socket is only ever touched by the backend process; it is never