Queued posts carry title, link card, and image through to publish

Summary

Closes the last queue gap: scheduled and drafted posts previously published with text only — the link preview, attached image, and explicit blog title were dropped at save time.

• New posts.content column persists { title?, external?, media? } as JSON
• Uploaded images are stored under storage/app/postline-media/ (gitignored) until publish; publish hydrates them back to bytes for the Bluesky blob upload, then deletes the file — deletes also clean up
• publish-now and the scheduled sweep pass the hydrated PublishContent through, so a scheduled blog post keeps its explicit title + full body, and a scheduled Bluesky post keeps its link card and image
• Queue items show image / link card badges

Bug found along the way

request.file('image') returns a raw Web File (the router's multipart parser stores File objects), not the typed FileInfo shape (buffer/mimetype) — so the publish action's image upload was silently dropping files too. A shared readUploadedImage helper now accepts both shapes; both actions use it.

Verification (live, authenticated)

• Save with title + link + image file → content JSON persisted, file on disk
• Publish-now → blog post has the explicit title with unstripped body; media file removed after success
• Delete a draft with an image → file removed from disk
• Queue list exposes hasImage/hasLink correctly
• bun test 21 pass, pickier clean, tsc --noEmit exit 0