v0.13.0 — Report tool : timestamped backups + manual revert

The previous deploy mechanism kept the old version under {target}.old
just long enough to swap, then deleted it — no way back if the new
report had a runtime bug only visible at use time.

Now each deploy keeps the previous active version under
{FolderName}.backup-yyyyMMdd-HHmmss/. The N most recent are kept
(MaxBackups, default 3) and older ones are pruned in best-effort.

UI in Settings → Avancés → Outil Report :
- "Conserver N backups" input (0 = no history, back to v0.12 behavior)
- List of backups with date + size + cryptic folder name + per-row "↶ Revert"
- Confirmation dialog: "Revert to {date}? The currently deployed
  version will itself be saved as a new backup, so you can switch back."

Implementation
- IReportToolDeployer: + ListBackupsAsync, + RevertAsync, + BackupInfo,
  + DeployStatus.BackupNotFound.
- ReportToolDeployer: deploy renames {target} → backup-{ts}; PruneOldBackups
  trims to MaxBackups; RevertAsync atomically swaps current ↔ chosen
  backup, the previous current becoming itself a fresh backup.
- ReportBackupViewModel + DataTemplate for the list rows.
- Strings: backup labels, "↶ Revert", confirmation message.

Caveats documented in the design discussion:
- Backups cover ONLY the report tool files. DB migrations are not reverted
  (irreversible). If a migration broke the schema, that's a separate fix.
- No HTTP-HEAD post-deploy auto-revert: too fragile for false positives.
  Revert stays a deliberate manual action.

Versions bumped to 0.13.0.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/PSLauncher.Models/LocalConfig.cs

@@ -107,6 +107,15 @@ public sealed class ReportToolConfig
     public string HtdocsRoot { get; set; } = @"C:\xampp\htdocs";
     public string FolderName { get; set; } = "ProserveReport";
     public bool AutoDeploy { get; set; } = true;
+
+    /// <summary>
+    /// Nombre de backups horodatés à conserver dans htdocs après chaque deploy.
+    /// Format des dossiers : <c>{FolderName}.backup-yyyyMMdd-HHmmss</c>.
+    /// Permet le revert via Settings si le nouveau deploy a un bug visible.
+    /// 3 par défaut = couvre les dernières releases sans grossir trop le disque.
+    /// 0 = pas de backup (retourne au comportement v0.12.0).
+    /// </summary>
+    public int MaxBackups { get; set; } = 3;
 }
 
 public sealed class LicenseConfig