[linstor-gui] Address coderabbit feedback on /healthz and reload annotation

- Fix /healthz Content-Type header: nginx silently drops `add_header`
  after `return` because the response is already finalized. Switch to
  `default_type text/plain;` placed BEFORE the `return 200` so the
  probe response is actually labeled as text/plain.
- Drop the redundant `checksum/nginx-config` pod-template annotation:
  the deployment already carries `reloader.stakater.com/auto: "true"`,
  so Stakater Reloader handles ConfigMap rollouts. Matches the sister
  `linstor` package convention.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Myasnikov Daniil <myasnikovdaniil2001@gmail.com>

packages/system/linstor-gui/templates/configmap-nginx.yaml

@@ -71,8 +71,11 @@ data:
 
         location = /healthz {
           access_log off;
+          # default_type must come BEFORE `return` — `add_header` after a
+          # `return` is silently dropped by nginx because the response is
+          # already finalized.
+          default_type text/plain;
           return 200 'ok';
-          add_header Content-Type text/plain;
         }
       }
     }

packages/system/linstor-gui/templates/deployment.yaml

@@ -18,8 +18,6 @@ spec:
       maxSurge: 1
   template:
     metadata:
-      annotations:
-        checksum/nginx-config: {{ include (print $.Template.BasePath "/configmap-nginx.yaml") . | sha256sum }}
       labels:
         {{- include "linstor-gui.labels" . | nindent 8 }}
     spec: