Upgrade to 1.0.0-rc804

Concerns: pushword/api, pushword/conversation, pushword/newsletter, pushword/quiz

API coverage and merge safety

• New GET /api/quiz/result and /api/quiz/result/stats read quiz attempts and per-quiz stats.
• Newsletter audiences get full CRUD over the API (/api/newsletter/audience[/{slug}]).
• Conversation import keeps the database row when the CSV row is strictly older and would change the content, and notifies the admin (a stale file rsynced over a production admin edit no longer silently wins). Hand-edited rows keep their exported updatedAt and still apply.