fix: copy dashboard package manifests from builder

[haosenwang1018]

Summary

• stop the dashboard production image from depending on package*.json being present in the final build context
• copy package.json and package-lock.json from the builder stage before running npm install --omit=dev

Why

Issue #134 reports docker compose up failing in the dashboard production stage with:

ENOENT: no such file or directory, open '/app/package.json'

The failure happens in the production stage at:

COPY package*.json ./
RUN npm install --omit=dev

Copying the package manifests from the already-populated builder stage makes the production stage self-consistent and avoids relying on the external build context for those files a second time.

Testing

• inspected the failing dashboard Docker stage from issue [BUG] docker compose up not working #134
• verified the patch keeps the production install step supplied with explicit package manifests from the builder stage

Closes #134

[nullure]

LGTM