Read a build log without fear

Open your project, click the latest deployment, then Building. The whole log is there.

• Scroll to the FIRST red line, not the last. Everything after it is usually a knock-on effect.
• Module not found means a file name or an import is wrong — check the capital letters, because Vercel's computers care about them and your laptop may not.
• A missing environment variable shows up as undefined, not as a clear error. Step 6 covers those.