fix(api): include collaborator invite status in notifications

[raymondjacobson]

Summary

• enrich track_collaborator_invite notification action data with the current track_collaborators.status at read time
• document collaborator notification types and optional action status in OpenAPI
• add a regression test for an invite notification whose collaborator row later becomes accepted

Test Plan

• go test ./api -run TestV1Notifications -count=1
• ruby -e "require 'yaml'; YAML.load_file('api/swagger/swagger-v1.yaml'); puts 'swagger yaml ok'"\n- git diff --check\n\n## Notes\nThis makes accepted collaborator invite notifications sticky after reload: the original invite notification row remains immutable, but the API now reads the canonical collaboration row and returns its current status.