feat(team): promote conversations into ad-hoc teams with continuous context

[DigitalNomad-Chat]

Description

This PR adds the AionCore backend support for promoting an existing conversation into an ad-hoc Team while preserving the source conversation relationship.

It includes:

• origin_conversation_id persistence and API response fields.
• Conversation-to-Team promotion service and routes.
• Leader/member conversation metadata using teamId and team_id.
• Team creation and lifecycle broadcasts for immediate client refresh.
• Team runtime/session association support.
• Teammate-message association and backflow support.
• SQLite unique-conflict mapping for origin conversation binding.
• Migration compatibility with the latest upstream baseline.

Related Issue

Related to AionUi issue #3574.

The companion AionUi PR is:

https://github.com/DigitalNomad-Chat/AionUi/pull/new/integrate/ad-hoc-team-latest

Type of Change

• feat — New feature
• fix — Related lifecycle and data-consistency fixes

Validation

• cargo test -p aionui-api-types
• cargo test -p aionui-db
• cargo test -p aionui-team
• Task-board integration tests
• cargo build -p aionui-team -p aionui-api-types
• No merge-tree conflicts with the latest upstream baseline.

Test results:

• aionui-api-types: 509 passed
• aionui-db: 271 passed
• aionui-team: 116 passed
• Task-board integration: 17 passed
• Doc tests: 0/0

Compatibility Notes

• The ad-hoc Team migration is numbered 028, following the upstream migration 027.
• AionUi should be upgraded together with this AionCore change because it consumes the new routes, fields, and lifecycle events.
• Existing normal Teams remain compatible when origin_conversation_id is absent.

Manual Verification Scenarios

• Promote an existing conversation into an ad-hoc Team.
• Confirm the source conversation is associated with the Team.
• Confirm leader and teammate conversation metadata are assigned correctly.
• Confirm Team creation events are broadcast to connected clients.
• Confirm teammate messages can be associated with the source conversation.
• Confirm Team removal retains enough origin information for navigation back.

Additional Context

The branch is based on the latest upstream AionCore baseline and has been independently validated against it. This PR should be reviewed together with the companion AionUi PR.