fix: replace Janitor wording with reclaim/prune actions in user-facing copy (#1518)

Rename "Janitor threshold" to "Reclaimable Docker data threshold" in Settings
and update the unused-Docker-data alert to point users to the Resources view
and the Prune Node Resources scheduled action, which are the real UI surfaces
for reclaiming disk space. Remove "janitor" from settings search keywords.
The internal docker_janitor_gb database key and JANITOR_* constants are
unchanged.

frontend/src/components/settings/DockerStorageSection.tsx

@@ -115,7 +115,7 @@ export function DockerStorageSection({ onDirtyChange }: DockerStorageSectionProp
         <fieldset disabled={readOnly} className="m-0 flex min-w-0 flex-col gap-10 border-0 p-0">
             <SettingsSection title="Storage alerts">
                 <SettingsField
-                    label="Janitor threshold"
+                    label="Reclaimable Docker data threshold"
                     helper="Alert when reclaimable Docker data exceeds this size."
                 >
                     <NumberChip

frontend/src/components/settings/registry.ts

@@ -195,7 +195,7 @@ export const SETTINGS_ITEMS: readonly SettingsItemMeta[] = [
         group: 'monitoring',
         label: 'Docker & Storage',
         description: 'Reclaimable-space alerts and Docker image cleanup after updates.',
-        keywords: ['docker', 'janitor', 'prune', 'reclaim', 'storage', 'images', 'cleanup', 'dangling'],
+        keywords: ['docker', 'prune', 'reclaim', 'storage', 'images', 'cleanup', 'dangling'],
         tier: null,
         scope: 'node',
     },