Add support for JetBrains Junie AI agent:
- Create .junie/guidelines.md with workflow instructions
- Create .junie/mcp/mcp.json for MCP server configuration
- Add 'junie' to BuiltinRecipes in recipes.go
- Add runJunieRecipe() handler in setup.go
- Add website documentation
- Add integrations/junie/README.md
Usage: bd setup junie
