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/de.json

@@ -33,7 +33,22 @@
     "previewTitlePlaceholder": "Embed-Titel",
     "previewDescriptionPlaceholder": "Embed-Beschreibung erscheint hier…",
     "clear": "Embed leeren",
-    "clearHint": "Leere Felder speichern kein Embed."
+    "clearHint": "Leere Felder speichern kein Embed.",
+    "advancedToggle": "Erweiterte Embed-Optionen (Author, Bilder, Footer)",
+    "authorSection": "Author (Kopfzeile)",
+    "authorNamePlaceholder": "Author-Name, z. B. {server}",
+    "authorIconPlaceholder": "Author-Icon-URL oder {server.icon}",
+    "authorUrlPlaceholder": "Author-Link (https://…)",
+    "mediaSection": "Medien",
+    "thumbnailPlaceholder": "Thumbnail-URL oder {user.avatar}",
+    "imagePlaceholder": "Großes Bild / Banner-URL (https://…)",
+    "titleUrlPlaceholder": "Titel-Link (https://…)",
+    "footerSection": "Footer",
+    "footerTextPlaceholder": "Footer-Text, z. B. Nexumi",
+    "footerIconPlaceholder": "Footer-Icon-URL oder {server.icon}",
+    "timestamp": "Zeitstempel anzeigen",
+    "timestampPreview": "gerade eben",
+    "mediaHint": "Bild-URLs müssen mit http(s) beginnen. Für Welcome kannst du {user.avatar} und {server.icon} nutzen."
   },
   "placeholders": {
     "toggle": "Verfügbare Platzhalter anzeigen",
@@ -59,7 +74,9 @@
       "feedTitle": "Titel des Feed-Eintrags",
       "feedUrl": "URL des Feed-Eintrags",
       "channelBracket": "Kanal-Erwähnung (Dashboard-Schreibweise, ID ersetzen)",
-      "channelNative": "Kanal-Erwähnung (Discord-Syntax, ID ersetzen)"
+      "channelNative": "Kanal-Erwähnung (Discord-Syntax, ID ersetzen)",
+      "userAvatar": "Avatar-URL des Mitglieds (für Thumbnail/Icons)",
+      "serverIcon": "Server-Icon-URL (für Author/Footer)"
     }
   },
   "nav": {