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/components/AddJobModal.tsx

@@ -118,6 +118,10 @@ export default function AddJobModal({ open, onClose, onCreated }: Props) {
   const [status, setStatus] = useState<(typeof STATUS_OPTIONS)[number]>("Applied");
   const [location, setLocation] = useState("");
   const [salary, setSalary] = useState("");
+  const [salaryMin, setSalaryMin] = useState("");
+  const [salaryMax, setSalaryMax] = useState("");
+  const [salaryCurrency, setSalaryCurrency] = useState("");
+  const [salaryPeriod, setSalaryPeriod] = useState("");
   const [jobUrl, setJobUrl] = useState("");
   const [deadline, setDeadline] = useState("");
 
@@ -291,6 +295,10 @@ export default function AddJobModal({ open, onClose, onCreated }: Props) {
         status,
         location,
         salary,
+        salaryMin: salaryMin.trim() ? Number(salaryMin) : null,
+        salaryMax: salaryMax.trim() ? Number(salaryMax) : null,
+        salaryCurrency: salaryCurrency.trim() || null,
+        salaryPeriod: salaryPeriod || null,
         nextAction: null,
         followUpAt: null,
         jobUrl,
@@ -482,6 +490,15 @@ export default function AddJobModal({ open, onClose, onCreated }: Props) {
           <TextField label={t("location")} value={location} onChange={(e) => setLocation(e.target.value)} sx={FIELD_SX} />
 
           <TextField label={t("addJobModalSalary")} value={salary} onChange={(e) => setSalary(e.target.value)} sx={FIELD_SX} />
+          <TextField label={t("salaryMinLabel")} type="number" value={salaryMin} onChange={(e) => setSalaryMin(e.target.value)} sx={FIELD_SX} />
+          <TextField label={t("salaryMaxLabel")} type="number" value={salaryMax} onChange={(e) => setSalaryMax(e.target.value)} sx={FIELD_SX} />
+          <TextField label={t("salaryCurrencyLabel")} value={salaryCurrency} onChange={(e) => setSalaryCurrency(e.target.value)} sx={FIELD_SX} inputProps={{ maxLength: 8 }} />
+          <TextField select SelectProps={{ native: true }} label={t("salaryPeriodLabel")} value={salaryPeriod} onChange={(e) => setSalaryPeriod(e.target.value)} sx={FIELD_SX} InputLabelProps={{ shrink: true }}>
+            <option value=""></option>
+            <option value="year">{t("salaryPeriodYear")}</option>
+            <option value="month">{t("salaryPeriodMonth")}</option>
+            <option value="hour">{t("salaryPeriodHour")}</option>
+          </TextField>
           <DatePicker
             label={t("addJobModalDeadline")}
             value={parsePickerDate(deadline)}