refactor: modernize report-to-backend action (#284)

- Replace abandoned `httpie` package (last release 2019) with native
  `fetch()`, eliminating deprecated `url.parse()` calls
- Add retry with exponential backoff for transient 5xx errors (3
  attempts at 2s/4s/8s) — this would have prevented the false
  failures seen on Apr 25 when the backend returned transient 500s
- Bundle with @vercel/ncc into a single dist/index.js, removing 298
  committed node_modules files from the repository
- Upgrade from node20 to node24, ahead of the June 2 2026 deadline
  when GitHub Actions will force node24 for all actions

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: frostebite

.github/workflows/actions/report-to-backend/action.yml

@@ -54,5 +54,5 @@ inputs:
     required: false
 
 runs:
-  using: 'node20'
-  main: 'index.js'
+  using: 'node24'
+  main: 'dist/index.js'