Rebrand to SegVision Engine, remove AI terminology, and fix video download extension headers

fix: resolve 'Failed to fetch' by hardening API URL detection and using same-origin relative paths

fix: unified deployment fix with flat routing, Suspense boundaries, and forced static export

fix: restore full content and wrap in Suspense for static build

fix: split dynamic routes into server+client components for static export

fix: resolve build-breaking JSX typos and add build robustness

chore: add HF Spaces Docker deployment

Initial commit — SegVision Video Segmentation App