fix(docker): build browser inference in dev stack

[JArmandoAnaya]

Summary

• include @visionset/browser-inference in the Compose app image and build it before Vite starts
• preserve built library output while watch builds run, preventing Vite from observing an empty ORT asset directory
• add a regression check for the Compose browser-inference build contract

Validation

• docker compose -f docker/compose.yaml -f docker/compose.gpu.yaml up --build -d
• app source and ORT asset served through nginx (HTTP 200)
• docker compose -f docker/compose.yaml -f docker/compose.gpu.yaml config --quiet
• node --test tests/scripts/compose_browser_inference.test.mjs

pnpm test:scripts requires a Node 24 checkout with local dependencies; the host checkout has neither.