[Feature] Improve MIME anonymization with LLM support and enhanced privacy

[Feature] Improve MIME anonymization with LLM support and enhanced privacy

- Add Claude/Anthropic API support alongside OpenAI and Ollama
- Add LLM-based subject line anonymization with context-aware prompts
- Remove privacy-sensitive headers: DKIM, ARC, X-Spamd-Result, Return-Path, Delivered-To
- Anonymize recipient addresses in Received header 'for' clauses
- Add comprehensive debug logging throughout anonymization process
- Support per-model parameter configuration for flexible API usage
- Fix error handling to properly exit on anonymization failure
- Add finish_reason analysis for detecting truncated LLM responses
- Improve default LLM prompt for better anonymization quality