feat(i18n): add new i18n message files and update request config

- Add new i18n message files: audit, course-plans, files, leave, nav, practice, scheduling, student, users

- Update existing i18n messages: ai, attendance, common, diagnostic, elective, error-book, exam-homework, grades, lesson-preparation, school, settings

- Update i18n request config for new locale handling

src/shared/i18n/messages/en/exam-homework.json

@@ -131,8 +131,9 @@
       "description": "Manage assignments, view submission rates and grading progress.",
       "create": "Create Assignment",
       "empty": "No assignments yet",
-      "emptyFiltered": "No assignments in this class.",
+      "emptyFiltered": "No assignments match your filters",
       "emptyDescription": "You haven't created any assignments yet.",
+      "emptyFilteredDescription": "Try clearing filters or adjusting keywords.",
       "clearFilters": "Clear filters",
       "filterByClass": "Filter by class: {{className}}",
       "columns": {