fix(salary): show the sysselsättningsgrad product next to the run salary input (#1702)

A Discord report had a 10 % employee: typing 4 531 in the run gave a
453,10 kr gross, so the user typed 45 310 to get it right. The engine was
correct (grundlön = månadslön × sysselsättningsgrad / 100) but nothing on
the row said so; the formula only lived in Beräkningsdetaljer. Below
100 % the row now prints "× 10 % = 4 531 kr" under the monthly salary
(input and read-only shapes), and both employee forms explain under
Sysselsättningsgrad that the base salary is monthly salary × degree.

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

messages/en.json

@@ -6703,6 +6703,7 @@
     "view_pdf": "View PDF",
     "view_payslip_title": "View payslip",
     "salary_input_aria": "Monthly salary for {name}",
+    "degree_hint": "× {degree} % = {amount}",
     "remove_sr": "Remove",
     "remove_employee_aria": "Remove {name} from the payroll run",
     "remove_employee_title": "Remove from the payroll run",
@@ -6937,6 +6938,7 @@
     "form_employment_start": "Employment start date",
     "form_employment_end": "End date",
     "form_employment_degree": "Degree of employment (%)",
+    "form_employment_degree_hint": "Below 100 % the base salary is monthly salary × degree of employment.",
     "form_hours_per_week": "Hours per week",
     "form_workdays_per_week": "Workdays per week",
     "form_work_schedule_hint": "The work schedule drives daily rates for absence and hourly-rate derivation (40 h / 5 days = default).",

messages/sv.json

@@ -6703,6 +6703,7 @@
     "view_pdf": "Visa PDF",
     "view_payslip_title": "Visa lönespecifikation",
     "salary_input_aria": "Månadslön för {name}",
+    "degree_hint": "× {degree} % = {amount}",
     "remove_sr": "Ta bort",
     "remove_employee_aria": "Ta bort {name} från lönekörningen",
     "remove_employee_title": "Ta bort från lönekörningen",
@@ -6937,6 +6938,7 @@
     "form_employment_start": "Anställningsdatum",
     "form_employment_end": "Slutdatum",
     "form_employment_degree": "Sysselsättningsgrad (%)",
+    "form_employment_degree_hint": "Under 100 % räknas grundlönen som månadslön × sysselsättningsgrad.",
     "form_hours_per_week": "Timmar per vecka",
     "form_workdays_per_week": "Arbetsdagar per vecka",
     "form_work_schedule_hint": "Arbetsschemat styr dagslön vid frånvaro och timlöneberäkning (40 h/5 dagar = standard).",