feat: add PolicyConfigurationForm functional component

[krisxcrash]

Summary

• Add PolicyConfigurationForm functional component that wraps PolicyConfigurationFormPresentation with the BaseComponent/useBase() pattern
• Integrates with useTimeOffPoliciesCreateMutation to create time-off policies via the embedded API
• Maps 3 form-level accrual methods (hourly, fixed, unlimited) to all 8 API accrual method variants, per Gusto accrual methods docs
• Converts numeric fields to API string format and formats policyResetDate as MM-DD
• Emits TIME_OFF_POLICY_DETAILS_DONE with { policyId } on success, CANCEL on back
• Exports the component and props type from the barrel index.ts

Accrual Method Mapping

Form selection	API accrual_method
Unlimited	unlimited
Hourly (default checkboxes)	per_hour_worked_no_overtime
Hourly + include overtime	per_hour_worked
Hourly + all paid hours	per_hour_paid_no_overtime
Hourly + both checked	per_hour_paid
Fixed + each pay period	per_pay_period
Fixed + all at once + calendar year	per_calendar_year
Fixed + all at once + anniversary	per_anniversary_year

Test plan

• Verify TypeScript compiles cleanly (npx tsc --noEmit)
• Verify existing presentation tests still pass
• Verify component renders in Storybook (no functional changes to presentation)
• Review accrual method mapping logic against API docs