feat: BYOK AI integration + Cloudflare model selector - Add runLLM/runLLMStream with tenant-aware AI routing - Support OpenAI, Anthropic, Kimi, Gemini, DeepSeek, custom endpoints - Add free Cloudflare model picker (Llama 3.3 70B, DeepSeek R1, Mistral) - Replace all 15 hardcoded AI calls with dynamic provider routing

Author: simpaticohr