Bundle size doubled with no obvious cause

1. Check the problem

Run `next build` for the route-level kB breakdown, then `npx @next/bundle-analyzer` for a visual. Usual culprits: a heavy library in a layout, a non-tree-shaken icon set, or a server-only module pulled into a client component.

2. Use the prompt

My Next.js bundle size jumped with no obvious cause. Show me how to read the route-level kB breakdown from next build and run the bundle analyzer, then help me find the culprit: a heavy lib imported in a layout, a non-tree-shaken icon set, or a server-only module pulled into a client component. Point at the import to change.

3. Verify the fix

Review the proposed diff, run the relevant checks and exercise the original failing flow before merging.