fix: hide date range in PayrollExecutionFlow for dismissal payrolls

[jeffredodd]

Summary

• Dismissal payrolls (offCycleReason === "Dismissed employee") don't have a meaningful pay period date range
• Hides the date range from the page description/subtitle, configuration breadcrumb label, and cancel dialog title when the payroll is a dismissal payroll
• Adds isDismissalPayroll() helper and date-free i18n keys, threads the flag through PayrollExecutionFlow to dynamically select breadcrumb labels

Test plan

• Verify dismissal payroll Configuration page shows "Dismissed employee payroll" without dates
• Verify dismissal payroll Overview page shows "Dismissed employee payroll" without dates
• Verify dismissal payroll cancel dialog shows "Cancel payroll?" without dates
• Verify dismissal payroll breadcrumb shows "Edit Payroll" without dates
• Verify regular and other off-cycle payrolls still show dates in all locations
• Existing payrollExecutionMachine tests pass (15/15)

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