Dune Analytics MCP Server

# Change: Add Core MCP Server Infrastructure ## Why The mcp-server-dune project requires a foundational FastMCP server with Dune Analytics client integration. This establishes the base architecture for all subsequent tools, resources, and prompts. ## What Changes - Initialize FastMCP server with proper metadata and dependencies - Create DuneClient factory with environment-based API key management - Establish project structure with proper Python packaging - Configure uv for dependency management with fastmcp.json ## Impact - Affected specs: core-server (new capability) - Affected code: server.py, fastmcp.json, pyproject.toml - Dependencies: fastmcp>=2.0.0, dune-client>=1.10.0, pydantic