feat(DayProduction, FalukantService, VocabLessonView): enhance vocabulary training and production tracking

- Added a new `completionCount` field to the DayProduction model to track the number of completed productions.
- Updated the FalukantService to aggregate completed productions using the new `completionCount` field, improving accuracy in production statistics.
- Introduced new vocabulary training features in VocabLessonView, including options to mark vocabulary as difficult and track remaining hard vocabulary, enhancing user engagement and learning effectiveness.
- Updated localization files for German and English to support new vocabulary training features, ensuring a consistent user experience across languages.

backend/models/falukant/log/dayproduction.js

@@ -23,7 +23,11 @@ DayProduction.init({
     productionDate: {
         type: DataTypes.DATEONLY,
         allowNull: false,
-        defaultValue: sequelize.literal('CURRENT_DATE')}
+        defaultValue: sequelize.literal('CURRENT_DATE')},
+    completionCount: {
+        type: DataTypes.INTEGER,
+        allowNull: false,
+        defaultValue: 1}
 }, {
     sequelize,
     modelName: 'DayProduction',

backend/services/falukantService.js

@@ -2968,7 +2968,9 @@ class FalukantService extends BaseService {
 
     /**
      * Zertifikat: abgeschlossene Produktionen über alle Regionen/Niederlassungen.
-     * Es zählt jede abgeschlossene Produktion (ein Datensatz in falukant_log.production).
+     * Es zählt jede abgeschlossene Produktion.
+     * Seit Daemon-Migration über falukant_log.production.completion_count
+     * (aggregierte Zeilen => SUM(completion_count), nicht COUNT(*)).
      * Filter bei gesetztem countSince wie Daemon (GET_PRODUCTION_CERTIFICATE_INPUT_ROWS):
      * COALESCE(production_timestamp, production_date::timestamp) >= countSince.
      *
@@ -2983,7 +2985,7 @@ class FalukantService extends BaseService {
         if (countSince) replacements.countSince = countSince;
         const rows = await sequelize.query(
             `
-            SELECT COUNT(*)::int AS cnt
+            SELECT COALESCE(SUM(COALESCE(completion_count, 1)), 0)::int AS cnt
             FROM falukant_log.production
             WHERE producer_id = :producerId${sinceClause}
             `,