Remove direct date_nav includes in favor of config-only approach
Delete apps/speakers/app_bar.html which was redundantly including
date_nav.html when the app already had date_nav: true in app.json.
Update APPS.md to document config-based enablement only.
๐ค Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>