feat: structured salary fields (min/max/currency/period)

Adds SalaryMin/SalaryMax/SalaryCurrency/SalaryPeriod alongside the
existing free-text Salary field (kept for back-compat and display).

- JobApplication model + idempotent column bridging for SQLite and MySQL
- Create/Update DTOs with NormalizeSalary (clamps negatives, swaps
  inverted min/max, uppercases currency, whitelists period)
- JobApplicationDto exposes the fields; CSV export gains 4 columns
- UI: add/edit dialogs get min/max/currency/period inputs; job table
  renders a formatted range via shared salary.ts formatter (falls back
  to free-text when structured values are absent)
- EN/NB translations; backend + full frontend suites green

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

job-tracker-ui/src/i18n/translations.ts

@@ -77,6 +77,13 @@ export const translations = {
     addJobModalStatus: "Status",
     addJobModalJobTitle: "Job title",
     addJobModalSalary: "Salary",
+    salaryMinLabel: "Salary min",
+    salaryMaxLabel: "Salary max",
+    salaryCurrencyLabel: "Currency",
+    salaryPeriodLabel: "Per",
+    salaryPeriodYear: "Year",
+    salaryPeriodMonth: "Month",
+    salaryPeriodHour: "Hour",
     addJobModalDeadline: "Deadline",
     addJobModalDescriptionOriginal: "Description (original)",
     addJobModalTranslatedDescription: "Translated description ({language})",
@@ -987,6 +994,13 @@ export const translations = {
     addJobModalStatus: "Status",
     addJobModalJobTitle: "Stillingstittel",
     addJobModalSalary: "Lønn",
+    salaryMinLabel: "Lønn fra",
+    salaryMaxLabel: "Lønn til",
+    salaryCurrencyLabel: "Valuta",
+    salaryPeriodLabel: "Per",
+    salaryPeriodYear: "År",
+    salaryPeriodMonth: "Måned",
+    salaryPeriodHour: "Time",
     addJobModalDeadline: "Frist",
     addJobModalDescriptionOriginal: "Beskrivelse (original)",
     addJobModalTranslatedDescription: "Oversatt beskrivelse ({language})",