1. Fix input fields in AI persona editor and make GitHub tool authentication optional
2. AI persona editor improvements and tool GitHub access token check
This pull request makes a few improvements:
- Adds `lang="en"` to number input fields in the AI persona editor to prevent localization issues
- Adds `step="any"` to allow fractional values for temperature and top_p settings
- Makes GitHub tool authentication contingent on `ai_bot_github_access_token` site setting being present
see: https://meta.discourse.org/t/ai-bot-personas-don-t-accept-decimals-for-temperature-top-p/298243/7
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