Refactor embed handling and enhance user experience across components

- Integrated the new `buildEmbedFromPayload` function in Scheduler, Tags, and Welcome components to streamline embed creation and management.
- Updated validation schemas to require embed content checks, ensuring robust data integrity for embeds.
- Enhanced localization files to include new placeholder descriptions and improve user guidance for embed fields.
- Refactored embed parsing logic to utilize the `WelcomeEmbedSchema`, improving consistency and validation across the application.

apps/webui/src/messages/en.json

@@ -33,7 +33,22 @@
     "previewTitlePlaceholder": "Embed title",
     "previewDescriptionPlaceholder": "Embed description appears here…",
     "clear": "Clear embed",
-    "clearHint": "Empty fields do not save an embed."
+    "clearHint": "Empty fields do not save an embed.",
+    "advancedToggle": "Advanced embed options (author, images, footer)",
+    "authorSection": "Author (header)",
+    "authorNamePlaceholder": "Author name, e.g. {server}",
+    "authorIconPlaceholder": "Author icon URL or {server.icon}",
+    "authorUrlPlaceholder": "Author link (https://…)",
+    "mediaSection": "Media",
+    "thumbnailPlaceholder": "Thumbnail URL or {user.avatar}",
+    "imagePlaceholder": "Large image / banner URL (https://…)",
+    "titleUrlPlaceholder": "Title link (https://…)",
+    "footerSection": "Footer",
+    "footerTextPlaceholder": "Footer text, e.g. Nexumi",
+    "footerIconPlaceholder": "Footer icon URL or {server.icon}",
+    "timestamp": "Show timestamp",
+    "timestampPreview": "just now",
+    "mediaHint": "Image URLs must start with http(s). For Welcome you can use {user.avatar} and {server.icon}."
   },
   "placeholders": {
     "toggle": "Show available placeholders",
@@ -59,7 +74,9 @@
       "feedTitle": "Feed item title",
       "feedUrl": "Feed item URL",
       "channelBracket": "Channel mention (dashboard syntax — replace the ID)",
-      "channelNative": "Channel mention (Discord syntax — replace the ID)"
+      "channelNative": "Channel mention (Discord syntax — replace the ID)",
+      "userAvatar": "Member avatar URL (for thumbnail/icons)",
+      "serverIcon": "Server icon URL (for author/footer)"
     }
   },
   "nav": {