Feat: Add meeting recording controller and webhook handler (Phase 4)

[jhodapp]

Description

Add meeting recording controller with start/stop endpoints and webhook handler for Recall.ai status updates. This enables coaches to start and stop meeting recordings during coaching sessions.

GitHub Issue: Relates to #146

Changes

• Add meeting_recording_controller with endpoints:
  • GET /coaching_sessions/:id/recording - Get recording status
  • POST /coaching_sessions/:id/recording/start - Start recording (coach only)
  • POST /coaching_sessions/:id/recording/stop - Stop recording (coach only)
• Add webhook_controller with POST /webhooks/recall for Recall.ai callbacks
• Export meeting_recording module from domain for CRUD operations
• Update router with recording and webhook routes
• Authorization checks ensure only the coach can control recordings
• Privacy level checks prevent recording when AI is disabled for the relationship

Testing Strategy

• Run cargo check and cargo clippy to verify compilation
• Run cargo test to ensure existing tests pass
• Manual testing requires:
  • Recall.ai API key configured in user integrations
  • Meeting URL configured for coaching relationship
  • Webhook URL configured for Recall.ai callbacks

Concerns

• This PR depends on Phase 3 (PR Feat: Add external API gateway clients and integration endpoints (Phase 3) #209) being merged first
• Webhook endpoint uses secret validation if WEBHOOK_SECRET is configured
• Real-time status updates via webhooks will update recording status in database