style: add consistent margin-bottom to content embeds

- Add 1rem margin-bottom to all embed types (url, iframe, video, image, gallery, audio, geolocation)
- Ensure YouTube embeds and URL cards have consistent spacing
- Prevent double margins when embeds are adjacent
- Matches the margin-bottom used for text blocks (paragraphs)

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/lib/components/edra/editor.css

@@ -572,3 +572,30 @@ input[type='checkbox'] {
 .tiptap iframe {
 	aspect-ratio: 16 / 9;
 }
+
+/* Content Embeds - Consistent spacing with text blocks */
+.tiptap .node-urlEmbed,
+.tiptap .node-iframe,
+.tiptap .node-video,
+.tiptap .node-image,
+.tiptap .node-gallery,
+.tiptap .node-audio,
+.tiptap .node-geolocation {
+	margin-bottom: 1rem;
+}
+
+/* YouTube embeds within urlEmbed */
+.tiptap .edra-youtube-embed-wrapper {
+	margin-bottom: 1rem;
+}
+
+/* URL embed cards */
+.tiptap .edra-url-embed-wrapper {
+	margin-bottom: 1rem;
+}
+
+/* Remove double margins if wrapper already has margin */
+.tiptap .edra-url-embed-wrapper + *,
+.tiptap .edra-youtube-embed-wrapper + * {
+	margin-top: 0;
+}