refactor(frontend,plugins): normalise les DTOs review backend et corrige le mock (#120)

- plugin.ts: normalizeReview() garantit issues/installable définis même si backend omet ces champs
- mock/index.ts: MockPluginGateway.uninstall() retourne removalOutcome pour cohérence avec le domaine
- domain/index.ts: PluginUninstallResult ajoute removalOutcome optionnel
- Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/domain/index.ts

@@ -1730,6 +1730,7 @@ export interface PluginInstallResult {
 /** Outcome of `uninstall`. */
 export interface PluginUninstallResult {
   pluginId: string;
+  removalOutcome?: "removed" | "tombstoned" | "notFound";
   restartRequired: boolean;
 }