feat(BillingService, BillingView): enhance locale handling for billing PDF generation

- Added methods to normalize and format numbers based on locale in BillingService, improving internationalization support.
- Updated _fillSessionRows and _renderBillingPdfFromTemplate methods to accept locale as a parameter for consistent number formatting.
- Modified BillingView to pass the current locale when generating billing PDFs, ensuring accurate representation of numerical values.

backend/services/billingService.js

@@ -30,6 +30,31 @@ const toMonthDate = (value, endOfMonth = false) => {
 };
 
 class BillingService {
+  _normalizeLocale(locale) {
+    const fallbackLocale = 'de-DE';
+    const raw = String(locale || '').trim();
+    if (!raw) return fallbackLocale;
+    const normalized = raw.replace('_', '-');
+    try {
+      const [resolved] = Intl.NumberFormat.supportedLocalesOf([normalized]);
+      if (resolved) return resolved;
+      const baseLanguage = normalized.split('-')[0];
+      const [resolvedBase] = Intl.NumberFormat.supportedLocalesOf([baseLanguage]);
+      return resolvedBase || fallbackLocale;
+    } catch (error) {
+      return fallbackLocale;
+    }
+  }
+
+  _formatNumberForLocale(value, locale, digits = 2) {
+    const numberValue = ensureNumber(value, 0);
+    return new Intl.NumberFormat(this._normalizeLocale(locale), {
+      minimumFractionDigits: digits,
+      maximumFractionDigits: digits,
+      useGrouping: false
+    }).format(numberValue);
+  }
+
   _resolveExistingFilePath(storedPath) {
     const rawPath = String(storedPath || '').trim();
     if (!rawPath) return null;
@@ -189,14 +214,14 @@ class BillingService {
     return { found, missing, availableFieldNames };
   }
 
-  _fillSessionRows(fieldEntries, sessions) {
+  _fillSessionRows(fieldEntries, sessions, locale = 'de-DE') {
     if (!Array.isArray(sessions) || !sessions.length) return;
     const rows = sessions.slice(0, 40);
     for (let idx = 0; idx < rows.length; idx += 1) {
       const rowNo = idx + 1;
       const row = rows[idx];
       const label = row.label || `${row.startTime || ''}-${row.endTime || ''}`.trim();
-      const hours = Number(row.durationHours || 0).toFixed(2);
+      const hours = this._formatNumberForLocale(row.durationHours || 0, locale, 2);
 
       const dateCandidates = [
         `date_${rowNo}`, `datum_${rowNo}`, `datum${rowNo}`, `lesson_date_${rowNo}`, `training_date_${rowNo}`, `zeile${rowNo}datum`
@@ -215,7 +240,7 @@ class BillingService {
     }
   }
 
-  async _renderBillingPdfFromTemplate(templatePath, outputPath, run, computedSessions, hoursTotal, amountTotal) {
+  async _renderBillingPdfFromTemplate(templatePath, outputPath, run, computedSessions, hoursTotal, amountTotal, locale = 'de-DE') {
     const templateBytes = fs.readFileSync(templatePath);
     const pdfDoc = await PDFDocument.load(templateBytes);
     const form = pdfDoc.getForm();
@@ -234,12 +259,10 @@ class BillingService {
     const locationValue = run.omitLocationText ? '' : (run.locationText || '');
     const dateValue = run.omitDocumentDate ? '' : (run.documentDate || '');
     const germanDateValue = this._toGermanDate(dateValue);
-    const hoursText = Number(hoursTotal || 0).toFixed(2);
-    const amountNumericText = Number(amountTotal || 0).toFixed(2);
+    const hoursText = this._formatNumberForLocale(hoursTotal || 0, locale, 2);
+    const amountNumericText = this._formatNumberForLocale(amountTotal || 0, locale, 2);
     const amountText = `${amountNumericText} EUR`;
-    const hourlyRateText = Number(run.hourlyRate || 0).toFixed(2);
-    const hourlyRateTextComma = hourlyRateText.replace('.', ',');
-    const amountNumericTextComma = amountNumericText.replace('.', ',');
+    const hourlyRateText = this._formatNumberForLocale(run.hourlyRate || 0, locale, 2);
 
     this._setByCandidates(fieldEntries, ['self_recipient_name', 'trainer_name', 'name_des_uebungsleiters', 'uebungsleiter', 'name'], nameValue);
     this._setByCandidates(fieldEntries, ['iban', 'konto', 'kontonummer'], ibanValue);
@@ -261,9 +284,9 @@ class BillingService {
     this._setByCandidates(fieldEntries, ['hours_total', 'gesamtstunden', 'summe_stunden', 'uestdn', 'u_stdn', 'dauer_summe', 'dauergesamt'], hoursText);
     this._setByCandidates(fieldEntries, ['hours_total_2', 'gesamtstunden2', 'summe_stunden2', 'dauer_abrechnung', 'dauerabrechnung'], hoursText);
     // First: explicit exact matches for this TSV Bonames form.
-    const hourlyExactSet = this._setByExactName(fieldEntries, 'gehalt_stunden', hourlyRateTextComma)
+    const hourlyExactSet = this._setByExactName(fieldEntries, 'gehalt_stunden', hourlyRateText)
       || this._setByExactName(fieldEntries, 'gehalt_stunden', hourlyRateText);
-    const amountExactSet = this._setByExactName(fieldEntries, 'gehalt_gesamt', amountNumericTextComma)
+    const amountExactSet = this._setByExactName(fieldEntries, 'gehalt_gesamt', amountNumericText)
       || this._setByExactName(fieldEntries, 'gehalt_gesamt', amountNumericText);
 
     if (!hourlyExactSet) {
@@ -275,7 +298,7 @@ class BillingService {
     }
     this._setByCandidates(fieldEntries, ['same_account_checkbox', 'same_account', 'gleicheskonto', 'gleiches_konto'], Boolean(run.sameAccountCheckbox), 'checkbox');
 
-    this._fillSessionRows(fieldEntries, computedSessions);
+    this._fillSessionRows(fieldEntries, computedSessions, locale);
 
     if (!diagnostics.found.length) {
       const fieldPreview = diagnostics.availableFieldNames.slice(0, 30).join(', ');
@@ -632,6 +655,7 @@ class BillingService {
       });
       return { status: 404, response: { success: false, error: 'Vorlagen-PDF nicht gefunden' } };
     }
+    const numberLocale = this._normalizeLocale(payload?.locale || payload?.language || payload?.lang);
     const computed = await this._collectTrainingSessions(run.clubId, run.periodStart, run.periodEnd);
     const sessionLabel = run.omitSessionLabel ? '' : String(run.sessionLabel || '');
     const sessionsWithLabel = computed.sessions.map((session) => ({
@@ -649,7 +673,8 @@ class BillingService {
       run,
       sessionsWithLabel,
       hoursTotal,
-      amountTotal
+      amountTotal,
+      numberLocale
     );
 
     const transaction = await sequelize.transaction();

frontend/src/views/BillingView.vue

@@ -1041,7 +1041,8 @@ export default {
         });
         const runId = createResponse.data?.run?.id;
         if (runId) {
-          const generateResponse = await apiClient.post(`/billing/runs/${runId}/generate`, {});
+          const locale = this.$i18n?.locale || 'de-DE';
+          const generateResponse = await apiClient.post(`/billing/runs/${runId}/generate`, { locale });
           if (!generateResponse.data?.success) {
             throw new Error(generateResponse.data?.error || 'PDF-Erzeugung fehlgeschlagen');
           }
@@ -1061,7 +1062,8 @@ export default {
       this.generatingRunIds.push(runId);
       this.feedback = { message: '', type: 'info' };
       try {
-        const response = await apiClient.post(`/billing/runs/${runId}/generate`, {});
+        const locale = this.$i18n?.locale || 'de-DE';
+        const response = await apiClient.post(`/billing/runs/${runId}/generate`, { locale });
         if (!response.data?.success) {
           throw new Error(response.data?.error || 'PDF-Erzeugung fehlgeschlagen');
         }
@@ -1078,7 +1080,8 @@ export default {
       this.generatingRunIds.push(runId);
       this.feedback = { message: '', type: 'info' };
       try {
-        const response = await apiClient.post(`/billing/runs/${runId}/generate`, {});
+        const locale = this.$i18n?.locale || 'de-DE';
+        const response = await apiClient.post(`/billing/runs/${runId}/generate`, { locale });
         if (!response.data?.success) {
           throw new Error(response.data?.error || 'PDF-Erzeugung fehlgeschlagen');
         }