feat(docs): add system prompt for LLM interaction

docs(readme): add comprehensive documentation for maccy clipboard mcp server

feat(config): add configurable server settings and defaults

feat(clipboard): improve text content handling and default limit

refactor(server): introduce shared database connection

feat(database): use shared database connection for all tool handlers

feat(clipboard): add get_item_content tool and improve existing handlers

docs(update readme): improve documentation for maccy-clipboard-mcp

feat(clipboard): implement maccy clipboard manager MCP server