Add TaxingWomen Bellman stage decomposition notebook

[jzhan476]

Notes on changes

• Revised TaxingWomen_bellman-stages.ipynb to make the Bellman representation more faithful to Taxing women: A macroeconomic analysis.
• Reworked the married-household problem into a clearer modular structure using the stages/perches framework from SolvingMicroDSOPs.
• Made the timing more explicit: female labor, male labor, consumption-savings, discounting, and the connector are now separated conceptually.
• Clarified the relationship between the paper's monolithic Bellman equation and the modular decomposition in the notebook.
• Added short explanatory text reflecting both class feedback and the AI critique, especially on timing, continuation structure, and the role of the disc stage and connector.