feat(db-repository): implement update message in MessageLifecycleRepository

[rafaeltonholo]

Stack

1. 3da3110 feat(db-repository): add domain models for messages, attachments, and thread messages #11593 (id: c-9653617)
2. 4c35913 chore(db-repository): convert message download operations to suspend functions #11604 (id: c-e9f0142)
3. [detached] 18b15b0 feat(core-architecture): add AsyncDataMapper interface for domain-DTO conversion #11606 (id: c-facc931)
4. 8a393e3 feat(db-repository): add DefaultMessageDataMapper for legacy-to-domain message conversion #11607 (id: c-9ed62a1)
5. f12481d feat(db-repository): add MessageQueryRepository for querying messages by criteria #11608 (id: c-be36e42)
6. f0da3d5 feat(db-repository): implement create message in MessageLifecycleRepository #11609 (id: c-639ad93)
7. 4f9accc feat(db-repository): implement update message in MessageLifecycleRepository (id: c-a66bc30) <-- current
8. 168347d feat(db-repository): implement move message in MessageLifecycleRepository #11611 (id: c-7f7af18)
9. 8506a59 feat(db-repository): implement copy and copyAll in MessageLifecycleRepository #11612 (id: c-145c77c)
10. b0d9b9f feat(db-repository): replace destroy with destroyAllByServerId and destroyByServerId #11613 (id: c-99f9e08) <- current

Contribution Summary

Linked Issue/Ticket: Part of #11486
RFC / Technical Design (if applicable):

Description

• Add update(message, accountId, folderId) to MessageLifecycleRepository with legacy adapter
• Add MessageAlreadyExists error and duplicate detection in create() via MessageQueryRepository
• Use create/update in K9BackendFolder.saveMessage, recovering from MessageAlreadyExists
• Use create/update in DraftOperations.saveDraftLocally
• Derive legacy download state from message flags in the mapper
• Add update and duplicate-detection tests to DefaultMessageLifecycleRepositoryTest

AI Disclosure

Select one of the following (mandatory)

• This contribution does not include any changes created or assisted by AI.
• This contribution includes changes assisted by AI.
• This contribution includes changes created by AI.

Contribution Checklist

• I have read and affirm that my contribution adheres to Mozilla’s Community Participation Guidelines
• This contribution is in Kotlin where possible
• This contribution does not use merge commits
• This contribution adheres to the existing codestyle (run gradlew spotlessCheck to check and gradlew spotlessApply to format your source code; will be checked by CI).
• This contribution does not break existing unit tests (run gradlew testDebugUnitTest; will be checked by CI).
• This contribution includes tests for any new functionality, and maintains tests for any updated functionality.
• This contribution adheres to our Engineering process (RFC/Technical Design/ADR)
• This PR has a descriptive title and body that accurately outlines all changes made, and contains a reference to any issues that it fixes (e.g. Closes #XXX or Fixes #XXX).