Add Thunderbolt integration page

[bilgeyucel]

https://github.com/thunderbird/thunderbolt/tree/main

[SyedShahmeerAli12]

Hello @bilgeyucel

Opened a PR for this: #452

What's included:

• integrations/thunderbolt.md — integration page (type: UI, via Hayhooks OpenAI-compatible endpoints)
• logos/thunderbolt.png — logo from the Thunderbolt repo