Implement maintenance mode and presence updates in bot and WebUI

- Added maintenance mode functionality in the bot, allowing for a custom message and DND status when enabled.
- Updated the OwnerPresencePage to include read-only access for VIEWER roles, with save permissions restricted to ADMIN roles.
- Enhanced the PresenceForm component to support immediate application of changes and added a confirmation for maintenance mode activation.
- Introduced localization updates for presence-related messages in both English and German, improving user guidance.
- Implemented a presence refresh queue to handle updates efficiently after configuration changes.

apps/webui/src/messages/en.json

@@ -1034,12 +1034,35 @@
     "presence": {
       "title": "Bot presence",
       "subtitle": "Status, activity, and maintenance mode.",
+      "editorTitle": "Edit presence",
+      "editorDescription": "Changes apply to the bot immediately after saving.",
+      "previewTitle": "Preview",
+      "previewRotatingHint": "Preview shows the first rotating line; Discord rotates about every minute.",
       "status": "Status",
       "activityType": "Activity type",
       "activityText": "Activity text",
+      "activityTextHint": "Fallback when no rotating messages are set.",
       "rotating": "Rotating messages (one per line)",
+      "rotatingHint": "Max. 20 lines of 128 characters. Rotates about every minute.",
       "maintenanceMode": "Maintenance mode enabled",
-      "maintenanceMessage": "Maintenance message"
+      "maintenanceMessage": "Maintenance message",
+      "maintenanceHint": "Slash commands will only reply with the maintenance notice.",
+      "maintenanceConfirm": "Really enable maintenance mode? Users will not be able to use commands.",
+      "maintenancePreviewBanner": "Maintenance mode: Discord shows DND and the maintenance text.",
+      "maintenanceFallbackActivity": "Maintenance",
+      "readOnly": "View only — saving requires Admin owner role or higher.",
+      "statusLabel": {
+        "online": "Online",
+        "idle": "Idle",
+        "dnd": "Do not disturb",
+        "invisible": "Invisible"
+      },
+      "activityTypeLabel": {
+        "Playing": "Playing",
+        "Listening": "Listening to",
+        "Watching": "Watching",
+        "Competing": "Competing in"
+      }
     },
     "team": {
       "title": "Team",