feat(editor): subtitle-first editor + AI subtitle pipeline

fix(hf-space): replace full app with minimal landing page

fix(hf-space): fix static dir path for SPA catch-all route

fix(hf-space): add HF Spaces config and root Dockerfile

feat(backend): implement Qwen2-VL visual analysis with ROCm support

fix(backend): raise burned subtitle placement

fix(backend): localize demo highlight text

feat(backend): enrich clipping pipeline metadata

feat(backend): add modular video processing API