Replace reload-after-save with optimistic in-place UI updates in speakers app
Remove delayed full sentence reloads after save/create voiceprint actions.
Update the affected sentence row in place by:
- setting the confirmed match label with checkmark
- disabling save controls to prevent double-save
- hiding the inline create form after successful creation
- inserting new entities into all speaker dropdowns (duplicate-safe via option iteration)
This eliminates both setTimeout(() => loadSentences(...), 1500) calls in saveVoiceprint and createEntityWithVoiceprint.