chore: enhance image reference resolution in updater script

- Added functionality to resolve image references with digests, improving the rollback process in the updater script.
- Updated health check URLs in targets.json.example to use service names instead of localhost, ensuring proper connectivity in containerized environments.

deploy/updater/targets.json.example

@@ -6,7 +6,7 @@
       "image": "git.shts.su/denozord/mikrotikmanager-backend:latest",
       "health": {
         "type": "http",
-        "url": "http://127.0.0.1:8000/health",
+        "url": "http://backend:8000/health",
         "expect_status": 200
       }
     },
@@ -16,7 +16,7 @@
       "image": "git.shts.su/denozord/mikrotikmanager-frontend:latest",
       "health": {
         "type": "http",
-        "url": "http://127.0.0.1:3000/",
+        "url": "http://frontend:3000/",
         "expect_status": 200
       }
     }