fix: Response wrapping, error logging, and controller hardening (COA 3)

- HttpExceptionFilter: Log actual error details for non-HttpExceptions (was silently swallowing 500s)
- ServersService: Return null fields instead of 404 for new licenses without servers
- NotificationsController: Wrap config responses as { config } to match frontend expectations
- WebstoreController: Wrap config responses as { config } to match frontend expectations
- ChatController: Replace ParseIntPipe with manual parseInt (400 on missing optional param)
- WipesController: Same ParseIntPipe fix for history limit param

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend-nest/src/modules/notifications/notifications.controller.ts

@@ -27,7 +27,8 @@ export class NotificationsController {
     description: 'Notification config retrieved successfully',
   })
   async getConfig(@CurrentTenant() licenseId: string) {
-    return await this.notificationsService.getConfig(licenseId);
+    const config = await this.notificationsService.getConfig(licenseId);
+    return { config };
   }
 
   @Put('config')
@@ -43,6 +44,7 @@ export class NotificationsController {
     @CurrentTenant() licenseId: string,
     @Body() dto: UpdateConfigDto,
   ) {
-    return await this.notificationsService.updateConfig(licenseId, dto);
+    const config = await this.notificationsService.updateConfig(licenseId, dto);
+    return { config };
   }
 }