ci: add timeout-minutes to the jobs in the two repaired workflows

While these two files are open for the startup_failure repair, add the
job-level timeout-minutes the estate convention (and Hypatia workflow_audit)
expects, clearing the missing_timeout_minutes findings for boj-build.yml and
changelog-reusable.yml at root. Scope kept to the files this PR already edits.

https://claude.ai/code/session_011xv3VLrqeXkpjXxUojKz82

Author: claude

.github/workflows/boj-build.yml

@@ -18,6 +18,7 @@ permissions:
 jobs:
   trigger-boj:
     runs-on: ubuntu-latest
+    timeout-minutes: 10
     if: ${{ vars.BOJ_SERVER_URL != '' || secrets.BOJ_SERVER_URL != '' }}
     steps:
       - name: Checkout

.github/workflows/changelog-reusable.yml

@@ -54,6 +54,7 @@ jobs:
   generate:
     name: Generate CHANGELOG.md
     runs-on: ${{ inputs.runs-on }}
+    timeout-minutes: 10
     permissions:
       contents: write
       pull-requests: write