feat: use xpier media library for uploads and markdown embeds

Store media:ID in post bodies instead of CDN URLs, and keep sablog attach tokens as a fallback.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/Filament/Resources/Media/MediaResource.php

@@ -27,6 +27,11 @@ class MediaResource extends Resource
 
     protected static ?string $pluralModelLabel = '媒体';
 
+    public static function shouldRegisterNavigation(): bool
+    {
+        return false;
+    }
+
     protected static ?string $model = Media::class;
 
     protected static string|BackedEnum|null $navigationIcon = Heroicon::OutlinedRectangleStack;