fix(docker): keep devDependencies out of production image

[iamlukethedev]

Summary

• add a production-focused multi-stage Dockerfile
• install prod-only dependencies in deps with npm ci --ignore-scripts --omit=dev
• install full deps separately in builder so npm run build still succeeds
• copy node_modules for runtime from deps (prod-only) instead of from builder

Issue verification

The reported issue is valid for the Dockerfile introduced in PR #82 (add-dockerfile):

• deps ran npm ci --ignore-scripts without --omit=dev
• runner copied node_modules from builder

That means devDependencies (Playwright, Vitest, ESLint, jsdom, etc.) ended up in the production image, increasing size and attack surface.

Result

The final runner image now contains only production dependencies while preserving a full dependency set where required for building.

Testing

• Verified Dockerfile stage wiring and copy sources so runtime receives prod-only node_modules.