add navigation, login, extraction workflow blocks

[LawyZheng]

[!IMPORTANT] Add NavigationBlock, ExtractionBlock, and LoginBlock to workflow models, YAML definitions, and service logic.

• Models:
  • Add NavigationBlock, ExtractionBlock, and LoginBlock classes in block.py.
  • Extend BlockType enum with NAVIGATION, EXTRACTION, and LOGIN.
  • Update BlockSubclasses union to include new block classes.
• YAML Definitions:
  • Add NavigationBlockYAML, ExtractionBlockYAML, and LoginBlockYAML classes in yaml.py.
  • Update BLOCK_YAML_SUBCLASSES to include new YAML block classes.
• Service Logic:
  • Update block_yaml_to_block() in service.py to handle new block types.
  • Add logic to convert YAML definitions to block instances for NavigationBlock, ExtractionBlock, and LoginBlock.

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