feat: Add optional RC branch support

[r-pedraza]

Pull Request

📝 Summary

This PR adds support for an optional release candidate (RC) branch configuration in the Git plugin, allowing users to specify an RC branch prefix.

🔧 Changes Made

• Added rc_branch parameter to GitClient initialization in git_client.py
• Updated GitPlugin to pass rc_branch from config in plugin.py
• Added rc_branch field to GitPluginConfig model in models.py

🧪 Testing

• Unit tests added/updated (poetry run pytest)
• All tests passing (make test)
• Manual testing with titan-dev

📊 Logs

• No new log events

✅ Checklist

• Self-review done
• Follows the project's logging rules (no secrets, no content in logs)
• New and existing tests pass
• Documentation updated if needed
• Plugin documentation updated when plugin functions or parameters changed (Plugins > Git Plugin, GitHub Plugin, Jira Plugin)

[finxo]

The Pydantic model TekelPluginConfig is defined twice in this file, once starting at line 131 and again at line 179. This duplication will likely cause runtime errors and should be removed. It seems to be an accidental copy-paste.