[ML 0.1/UI.04.2] - Implement legacy message list loading bridge

[rafaeltonholo]

Blocked by

• [ML 0.1/UI.04.1] - Migrate MessageListFragment to Compose-based renderer #10774

Description

Implement the bridge between the legacy message loading system and the Compose UI. This includes creating the LegacyMessageListBridge interface, the LoadMessagesLegacySideEffect that invokes the bridge to load messages from the legacy data source, and the mapping from MessageListItem to MessageItemUi.

Acceptance Criteria

• LegacyMessageListBridge interface defined in the API module.
• LoadMessagesLegacySideEffect loads messages from legacy and maps them to MessageItemUi.
• MessageItemUi includes messageReference for identifying messages.
• MessageListFragment implements the bridge, converting MessageListItem -> MessageItemUi.
• Manual refresh on sort criteria change is removed (handled by bridge).
• Action mode finish is guarded to only trigger when inactive and no messages are selected.
• New state feature is enabled alongside Compose for message list items.
• Unit tests for LoadMessagesLegacySideEffect.