bug: Nightly Performance Baseline workflow pushes commits to forks

[yehudit1987]

Describe the bug

Problem

The performance-nightly.yml workflow runs on forks and pushes commits to the fork's main branch, causing it to diverge from upstream.

Suggested Fix

Add repository condition to .github/workflows/performance-nightly.yml:

jobs:
update-baseline:
runs-on: ubuntu-latest
if: github.repository == 'vllm-project/semantic-router'

To Reproduce

1. Fork the vllm-project/semantic-router repository
2. Keep GitHub Actions enabled on the fork (default)
3. Wait for the nightly schedule (3 AM UTC) or trigger the workflow manually
4. Observe that a commit chore: update performance baselines (nightly run) is pushed to the fork's main branch
5. Fork now shows "X commits ahead of vllm-project:main"

Expected behavior

No response

Additional context

No response

[szedan-rh]

@yehudit1987 - Thank you for the fix, after thinking about this change i have disable the nightly check and keep the performance check for each PR that raise as part of CI tests:
#836