fix(exam): stop Create/Update Exam form from silently failing to submit

Three bugs compounded into a button that looked unwired:

- cuttingPoint carried a native HTML required attribute while sitting on
  the hidden Settings tab (Mantine keeps inactive tab panels mounted with
  display:none). The browser blocked form submission entirely, silently
  - no toast, no error, nothing. Replaced required with withAsterisk and
  moved validation into JS.
- Manual required-field validation never checked type/form/adminMethod/
  evalMethod/cuttingPoint at all, so even without the native block above
  a half-filled Settings tab would silently no-op. Validation now covers
  every required field on both tabs and switches to whichever tab has
  the problem.
- Filling only the English Direction field (leaving Amharic blank) passed
  frontend validation but the backend hard-rejects it, producing a 400
  with a confusing error. Frontend now requires both-or-neither, matching
  the same rule already applied to MCQ options.

Also translates the previously hardcoded validation message in both
locales.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/backoffice/src/app/features/exam/pages/ExamPage/index.tsx

@@ -77,21 +77,23 @@ function ExamForm({
     editing?.cuttingPoint ?? 0,
   );
   const [status, setStatus] = useState<string | null>(editing?.status ?? null);
+  const [activeTab, setActiveTab] = useState<string | null>("basic");
 
   const handleSubmit = (e: React.FormEvent) => {
     e.preventDefault();
-    if (
-      !certificationId ||
-      !titleEn ||
-      !titleAm ||
-      !date ||
-      !type ||
-      !form ||
-      !venue ||
-      !adminMethod ||
-      !evalMethod
-    ) {
-      notify.error("Please fill all required fields");
+    if (!certificationId || !titleEn || !titleAm || !date || !venue) {
+      setActiveTab("basic");
+      notify.error(t("exam.form.fillRequiredBasic"));
+      return;
+    }
+    if ((directionEn || directionAm) && !(directionEn && directionAm)) {
+      setActiveTab("basic");
+      notify.error(t("exam.form.directionBothLanguages"));
+      return;
+    }
+    if (!type || !form || !adminMethod || !evalMethod || !cuttingPoint) {
+      setActiveTab("settings");
+      notify.error(t("exam.form.fillRequiredSettings"));
       return;
     }
     onSubmit(
@@ -121,7 +123,7 @@ function ExamForm({
   return (
     <Modal opened onClose={onCancel} title={editing ? t("exam.update") : t("exam.add")} size="xl">
       <form onSubmit={handleSubmit}>
-        <Tabs defaultValue="basic" variant="outline" radius="md">
+        <Tabs value={activeTab} onChange={setActiveTab} variant="outline" radius="md">
           <Tabs.List mb="md">
             <Tabs.Tab value="basic" leftSection={<IconInfoCircle size={15} />}>
               {t("exam.form.basicInfo")}
@@ -296,7 +298,7 @@ function ExamForm({
                   onChange={(v) => setCuttingPoint(Number(v))}
                   min={0}
                   size="sm"
-                  required
+                  withAsterisk
                 />
               </SimpleGrid>
               {editing && (