feat(email-service): Per-message contact name storage

[evanhutnik]

Summary

This PR adds per-message contact name storage to preserve the exact sender and recipient names as they appear in each email.

Changes:

• Added from_name column to email_messages to store the sender's name as it appears in the message
• Added name column to email_message_recipients to store recipient names as they appear in the message
• Updated thread/message/preview APIs to prioritize message-specific names, falling back to email_contacts names when unavailable

Background:

Previously, we avoided storing contact names for generic emails in email_contacts due to an edge case where personal names could be associated with shared addresses:

This led to incorrect name display when multiple people used the same email address.

By storing names on a per-message basis, we now correctly handle this scenario—each message displays the name as it appeared when sent.

Migration & Backfill:

The migration includes a backfill for existing messages where possible. However, as mentioned, generic email names processed before this change were intentionally not stored in email_contacts and cannot be fully recovered. Rather than re-processing 6.7 million messages across 444 accounts, new messages going forward will have complete name data. Existing messages will show names where available in email_contacts. There is already logic in the FE to handle the case where no name exists for the contact, so this shouldn't result in any weird behaviour.

Screenshots, GIFs, and Videos

[linear]

EMA-45 Create one row per recipient per email for contacts