- config/engine.json: switch video_generation provider from sora to
smart_router; add kling_free/veo3/seedance2 engine options; update
optional_keys (KLING_API_KEY, FAL_API_KEY); keep legacy entries
- bots/converters/smart_video_router.py: new SmartVideoRouter class with
budget-aware engine selection, daily state tracking, Kling stub
implementation, and ffmpeg_slides fallback chain
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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