Richer writing: media picker & paste-to-format

The blog editor now meets you where you write.

• Choose from media — the image dialog opens your media library so you pick an existing upload instead of hunting for a URL.
• Paste rich text from a web page or Google Docs and keep the formatting — bold, italics, links, headings, lists, and images all carry over.
• Everything still round-trips to clean Markdown, so nothing is stored as HTML.