feat: VOD recording recovery for orphaned streams (#552)

[filthyrake]

Summary

• Adds background recovery loop that detects streams stuck in ended state with auto_record_vod=true and vod_video_id IS NULL, and retries VOD creation
• Adds 3 config variables: LIVE_VOD_RECOVERY_INTERVAL (120s), LIVE_VOD_RECOVERY_GRACE_PERIOD (300s), LIVE_VOD_RECOVERY_MAX_RETRIES (5)
• In-memory retry tracking per stream, with max retries and one-time error log at exhaustion
• Addresses Copilot PR review feedback from fix: Verify stream state before triggering VOD recording (#552) #569: wraps re-fetch in try/except, uses original auto_record_vod flag for VOD decision
• Adds (id=...) to VOD error log messages for easier debugging

Test plan

• 12 unit tests in tests/test_vod_recovery.py all pass
• Verify recovery loop starts/stops with background tasks
• Verify orphaned streams get VOD created after grace period
• Verify streams at max retries are skipped

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