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/leave.json

@@ -0,0 +1,12 @@
+{
+  "title": "Leave Request",
+  "description": "Submit a leave request for your child.",
+  "backToDashboard": "Back to Dashboard",
+  "onlineLeave": "Online Leave Request",
+  "comingSoon": "Coming soon",
+  "comingSoonDesc": "The online leave request feature is being developed and will be available soon. For now, please contact the homeroom teacher or school office directly.",
+  "contactOptions": "Contact options",
+  "callOffice": "Call the school office during working hours",
+  "sendMessage": "Send a message to the homeroom teacher via the Messages page",
+  "goToMessages": "Go to Messages"
+}