Feature: Unread message indicators for channels

[mjkatgithub]

Goal

Make channels with unread messages clearly visible in the channel list.

Scope

• Detect unread state per channel based on latest read marker.
• Show a visible unread indicator in the channel list item.
• Keep indicator state in sync on new messages and when channel is opened.
• Persist and restore unread state correctly after reload.
• Ensure unread indicator works alongside existing room ordering/filtering.

Branch

feature/unread-channel-indicators

Acceptance Criteria

• A channel with unread messages is clearly marked in the list.
• Opening/reading a channel clears the unread indicator correctly.
• New incoming messages update unread state without manual reload.
• Unread indicator state survives app reload with correct values.
• Existing channel list behavior remains stable.

Test Checklist

Unit

• Unread state calculation from read marker and latest event.
• State transitions for read/unread updates.

Integration

• Channel list rendering reflects unread state changes.
• Sync/update flow applies unread state after incoming events.

E2E

• Send message to a non-active channel and verify unread mark.
• Open marked channel and verify unread state is cleared.
• Reload app and verify unread markers are still correct.

Notes

• Keep visual treatment accessible and noticeable in both themes.