Add configurable capacity-calculation rules for inspector balance

Add configuration and override support for how inspector capacity is calculated in the inspector balance widget.

Summary

This is a supplement to the current inspector balance widget work being delivered in Attik-Field-Service-Solutions/attik-backend#499 and Attik-Field-Service-Solutions/attik-frontend#665.

Requirements

1. Add a company-wide configuration for what counts in the numerator / denominator per inspector:

• inspections only
• inspection events only
• blended (combination of inspections and inspection events)

1. Add per-inspector support for grouping multiple time slots as a single availability window when computing denominator capacity.
2. Add an inspector settings field for a manual denominator override that replaces the computed denominator entirely when set.

• This override is not additive.
• It is not a floor or ceiling.
• It fully replaces the computed denominator.

Context

The current open PRs improve the widget UX and filtering behavior for capacity planning, but these additional requirements change the underlying calculation model itself. They should be tracked separately so the calculation rules, settings surfaces, and override behavior can be implemented explicitly.

These requirements are closely related to the current capacity-planning work on ATT-1593.