grafana-renderer Error cannot find module app.js

Just noticing this error now in a crash-looping granfana-renderer.

```
node:internal/modules/cjs/loader:1404
throw err;
^

Error: Cannot find module '/home/nonroot/build/app.js'
at Function._resolveFilename (node:internal/modules/cjs/loader:1401:15)
at defaultResolveImpl (node:internal/modules/cjs/loader:1057:19)
at resolveForCJSWithHooks (node:internal/modules/cjs/loader:1062:22)
at Function._load (node:internal/modules/cjs/loader:1211:37)
at TracingChannel.traceSync (node:diagnostics_channel:322:14)
at wrapModuleLoad (node:internal/modules/cjs/loader:235:24)
at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:171:5)
at node:internal/main/run_main_module:36:49 {
code: 'MODULE_NOT_FOUND',
requireStack: []
}

Node.js v22.17.1
```

Image version:
```
docker.io/grafana/grafana-image-renderer@sha256:50347baa45da86ecb577c1838ba18304e0e6af7379eda93580e6d6685b7f4a8f
```

Start by reproducing the crash with the reported grafana-image-renderer image digest and inspect its container entrypoint and build output. Trace why /home/nonroot/build/app.js is absent, then verify that the renderer starts without the crash loop using a corrected image or configuration.

Written by the indexing model from the issue text.