Broadcasts: one design with a version per language, sent to each contact in their locale #203

What happened

An email design holds text in a single language, and a broadcast's locales only filters who receives it. To send the same newsletter to contacts who speak Portuguese, Spanish, French and Turkish, a workspace has to duplicate the design once per language, translate each copy, and create one broadcast per language with its own locales filter. The copies drift apart when the layout or logo changes, and the reports are split across several broadcasts.

What I expected

A design can hold a translation of its text blocks (and subject and preheader) per language, with a fallback language. A single broadcast sends each contact the version matching their locale (exact tag, then base language, e.g. es-mx → es), and the fallback to contacts with no locale or no matching version. Layout, images and links stay shared. The broadcast report can be read as a whole and per language. The MCP tools (create_design, update_design, preview_design, create_broadcast_draft) take a locale for reading and writing a version.

Steps to reproduce

1. Have contacts on one list with locales pt, es-mx, fr and tr.
2. Create a design from a template; it has one language.
3. Create a broadcast to the list: every contact gets the same language, or locales has to narrow it to one language per broadcast.

Environment

• Yuva server: 0.0.1-de686e0
• Area: broadcasts

_{Prepared by an AI assistant with the Yuva MCP tool report_yuva_issue. Names, addresses, keys, ids and local paths were removed before the person reviewed it.}