Messages size at once; quoted inline images travel inside the reply

The message frame is set up as soon as its document is parsed instead of at
its load event, which waits for every image (remote ones included): it no
longer sits at its first height until the slowest image arrives.

A reply quoted an original's inline (cid:) images as this server's own URLs,
and they were sent like that — broken for the recipient, and mangled copies
("http:///api/…") made browsers look up a host named "api". Outgoing mail
(and the IMAP Drafts copy) now carries them as inline parts with new
Content-IDs; one that can no longer be had is left out. Shown messages load
such URLs from this server (sanitizer v5).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

backend/app/outbox/draft_sync.py

@@ -17,6 +17,7 @@ from sqlalchemy import select
 
 from app.db import session_scope
 from app.models import Account, Draft, Mailbox, Message
+from app.outbox import inline_images
 from app.outbox.attachments import load_attachments
 from app.outbox.mime_build import build_mime
 from app.sync.provider_factory import build_provider
@@ -68,7 +69,15 @@ async def push_draft_to_imap_job(ctx: dict[str, Any], draft_id: str) -> None:
             else None
         )
         attachments = await load_attachments(session, user_id, draft)
-        _, sent_raw, _, _ = build_mime(account, draft, reply_to, attachments)
+        html, inline = await inline_images.embed(
+            session,
+            user_id,
+            str(draft.payload.get("html", "") or ""),
+            account.email.rsplit("@", 1)[-1],
+        )
+        _, sent_raw, _, _ = build_mime(
+            account, draft, reply_to, attachments, html=html, inline=inline
+        )
         drafts_mb = await session.scalar(
             select(Mailbox).where(Mailbox.account_id == account.id, Mailbox.special_use == "drafts")
         )