feat: Add DFF commands

[fredvisser]

Core Features

• Complete DFF command suite: dff config, dff groups, dff fields, dff tables with full CRUD operations
• Web-based editor: Standalone HTML editor with local HTTP server for DFF configuration authoring
• Enhanced error handling: Context-aware error parsing for partial failures with detailed validation messages
• Performance optimization: Single workspace map retrieval eliminating redundant API calls

Key Components

• dff_click.py (1,047 lines): Main DFF command implementation with create/update/delete/list/export/init operations
• web_editor.py (464 lines): Local web server and HTML editor for DFF configurations
• Comprehensive testing (667 lines): Full test coverage for all DFF operations
• Documentation updates: README with usage examples and web editor instructions

Technical Highlights

• PEP8-compliant code with full type hints and docstrings
• Standardized error handling with appropriate exit codes
• JSON/table output formats with consistent formatting
• Workspace filtering and cross-platform compatibility
• Template generation for new DFF configurations