Add deprecation notice to README

[murrayju]

Summary

• Added a deprecation notice to the README informing users that this MCP server is no longer maintained
• Recommended users migrate to alternative memory solutions
• Included a note to open issues for questions or migration assistance

Test plan

• Review the updated README to ensure the deprecation notice is clear and appropriately placed

🤖 Generated with Claude Code

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[murrayju]

This was just testing an agent for PR creation, disregard.