Auto summarize conversations, add attachment count

[Josh-XT]

This pull request introduces enhancements to the conversation management and database schema in the agixt project. The key changes include adding support for conversation summaries and attachment counts, updating the database schema to include these new fields, and ensuring the conversation summary is updated during interactions.

Enhancements to conversation management:

• agixt/Conversations.py: Added methods set_conversation_summary, get_conversation_summary, get_attachment_count, update_attachment_count, and increment_attachment_count to manage conversation summaries and attachment counts.
• agixt/Conversations.py: Updated get_conversations_with_detail to include summary and attachment_count in the returned conversation details.

Database schema updates:

• agixt/DB.py: Added summary and attachment_count columns to the Conversation class.
• agixt/DB.py: Implemented ensure_conversation_summary function to add the new columns to the database schema if they do not already exist. [1] [2]

Conversation summary updates:

• agixt/XT.py: Incremented attachment count when a file is downloaded in learn_from_file.
• agixt/XT.py: Updated the conversation summary after a chat completion in chat_completions.

New prompt template:

• agixt/prompts/Default/Summarize Conversation.txt: Added a new prompt template for summarizing conversations.