chore: add explicit permissions to GitHub Actions workflows (#3807)

Fixes code scanning alerts #1, #2, #3, #4
(actions/missing-workflow-permissions).

- retry-workflow.yml rerun job: actions: write (to rerun workflows)
- upload-to-r2.yml upload-to-r2 job: contents: read (to download releases)
- upload-to-r2.yml retry-on-failure job: actions: write (to trigger retry)
- release.yml upload-to-r2 job: contents: read, actions: write

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/workflows/retry-workflow.yml

@@ -8,6 +8,8 @@ on:
 jobs:
   rerun:
     runs-on: ubuntu-latest
+    permissions:
+      actions: write
     steps:
       - name: rerun ${{ inputs.run_id }}
         env: