fix: Switch to FAISS as default and use /tmp for persist directory

feat: Add Groq-optimized prompts, vector DB fallback, improved ignore patterns

fix: Add ChromaDB auto-recovery from corruption

feat: Add local embeddings to bypass API rate limits

feat: Add MCP + CrewAI integration with multi-mode interface

Refactor: Upgraded to Agentic Chatbot with AST & Call Graph support