v0.12.2: restore section simplification — snapshot filtering, auto-stop/restart, UI cleanup

- StackDataProvider interface extended with StopStack/StartStack
- backup.Manager.GetStackHDDMounts() delegates to stackProvider
- RestoreApp() auto-stops app before restic restore, restarts after (even on failure)
- stackAdapter in main.go wires StopStack/StartStack through to stacks.Manager
- GET /api/backup/snapshots?stack={name} filters snapshots by app HDD paths via filterSnapshotsByPaths()
- Restore section simplified: no path list, per-app filtered snapshots, human-friendly timestamp format, single calm warning, empty-result inline message

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

controller/README.md

@@ -24,7 +24,7 @@ controller generates secrets, saves app.yaml, runs `docker compose up -d`, and t
 with Traefik routing and health checks. The dashboard correctly shows real-time container states
 including health substatus (starting → healthy → running).
 
-Current version: **v0.10.0**
+Current version: **v0.12.2**
 
 ### What works
 - Dashboard with live container state (green/orange/yellow/red)