dx(frontend): Fix source map upload configuration (#11378)

Source maps aren't being uploaded to Sentry, so debugging errors in
production is really hard.

### Changes 🏗️

- Fix config so source maps are found and uploaded to Sentry
- Disable deleting source maps after upload (so they are available in
the browser)

### Checklist 📋

#### For code changes:
- [x] I have clearly listed my changes in the PR description
- [x] I have made a test plan
- [x] I have tested my changes according to the test plan:
  - [x] Tested locally

autogpt_platform/frontend/next.config.mjs

@@ -80,10 +80,10 @@ export default isDevelopmentBuild
 
       // This helps Sentry with sourcemaps... https://docs.sentry.io/platforms/javascript/guides/nextjs/sourcemaps/
       sourcemaps: {
-        disable: false, // Source maps are enabled by default
-        assets: ["**/*.js", "**/*.js.map"], // Specify which files to upload
-        ignore: ["**/node_modules/**"], // Files to exclude
-        deleteSourcemapsAfterUpload: true, // Security: delete after upload
+        disable: false,
+        assets: [".next/**/*.js", ".next/**/*.js.map"],
+        ignore: ["**/node_modules/**"],
+        deleteSourcemapsAfterUpload: false, // Source is public anyway :)
       },
 
       // Automatically tree-shake Sentry logger statements to reduce bundle size