Remove position-budgets source feature flag (local source now in prod)

[rmartinsen-ucd]

Now that the local/pipelined position-budgets source is live in production, the PositionBudgets__Source feature flag and the legacy code path it guards can be retired.

Background

The flag was added to switch the personnel/position-budgets data source between the legacy Oracle path and the new local table:

• Config: DatamartOptions.PositionBudgetsSource (env var PositionBudgets__Source), values UCPathDWH (default) vs Local.
• Dev defaulted to Local; Prod opted in via an Azure App Setting.
• Local path: usp_GetPositionBudgetsLocal (reads dbo.PositionBudgets).
• Legacy path: usp_GetPositionBudgets (Oracle / OPENQUERY).

Prod is now on the local source, so the toggle is no longer needed.

Cleanup checklist

• Remove the PositionBudgetsSource option from DatamartOptions and any IOptions wiring / branching that selects the source.
• Default the app to the local source unconditionally (drop the UCPathDWH branch).
• Remove the PositionBudgets__Source app setting from Azure (Dev/Test/Prod) once the code no longer reads it.
• Delet the legacy usp_GetPositionBudgets (Oracle/OPENQUERY) sproc
• Update/trim tests that exercised the flag.

Notes

• Confirm prod has been stable on the local source before removing the fallback.