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.Updater/PSLauncher.Updater.csproj

@@ -8,7 +8,7 @@
     <LangVersion>latest</LangVersion>
     <AssemblyName>PSLauncher.Updater</AssemblyName>
     <RootNamespace>PSLauncher.Updater</RootNamespace>
-    <Version>0.12.0</Version>
+    <Version>0.13.0</Version>
     <ApplicationIcon>..\PSLauncher.App\Resources\favicon.ico</ApplicationIcon>
     <Company>ASTERION VR</Company>
     <Copyright>© 2026 ASTERION VR — All rights reserved</Copyright>