[Backlog] Add Genie pricing workloads

[CheeYuTan]

Summary

Add first-class Lakemeter estimation for the Genie product family shown in the Databricks pricing catalog:

• Genie One — Enterprise Knowledge
• Genie Spaces — Natural Language Q&A
• Genie Code — AI Coding Assistant

Scope

• Verify whether the three Genie products share or differ in DBU rates, free allowances, usage units, and availability.
• Model the billable LLM usage with practical monthly planning inputs.
• Represent free usage explicitly rather than hiding it in an effective rate.
• Keep additive compute, such as SQL Serverless used by Genie Spaces, separate and clearly explained.

Acceptance criteria

• Add appropriate Genie workload type(s), calculation API, and frontend forms.
• Resolve exact regional SKU pricing and free allowances without fallback.
• Persist all inputs in workload_config; no database schema migration.
• Show transparent usage → free allowance → billable DBUs → cost formulas.
• Include AI-assisted estimate creation, cloning, and Excel export.
• Show additive/excluded SQL compute and other service costs in the UI.
• Add calculation, validation, persistence, parity, and export tests.
• Validate assumptions against current official pricing before release.

Reference

• https://www.databricks.com/product/pricing/genie