feat(settings): Copy + Download buttons for config preview

v1.1.100

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

management-ui/src/i18n/locales/en/common.json

@@ -596,6 +596,7 @@
     "configPreviewCardTitle": "Config preview",
     "configPreviewBtn": "Load preview",
     "configPreviewHint": "Renders the selected service config from the current DB state. Read-only — nothing is written to disk or reloaded.",
+    "configCopied": "Config copied to clipboard",
     "passwordCardTitle": "Change admin password",
     "currentPassword": "Current password",
     "newPassword": "New password",