Add Groq as a provider

[8crsk]

Groq's API is OpenAI-compatible and famously fast — a great fit for an interactive phone agent.

Where: app/src/main/java/com/crsk/openclaw/data/providers/ProviderCatalog.kt — follow the pattern of the four existing CUSTOM providers (see also the sibling issue for OpenRouter).

Acceptance criteria

• groq entry (baseUrl https://api.groq.com/openai/v1, default models e.g. llama-3.3-70b-versatile)
• Key hint/validation (gsk_…)
• Works end-to-end from Settings
• Tests + lint green