feat(platform): ship AI fallback stack and entity-scoped course planning

Unifies the new LangGraph-driven course-plan/media flow with robust provider fallbacks, admin AI provider settings, editable book-style materials, and strict entity isolation across LMS/course-plan APIs. Adds admin-only entity membership management in the Entities UI so users can switch linked entities directly from the platform.

Made-with: Cursor

src/pages/student/ExamSession.tsx

@@ -40,10 +40,23 @@ function buildAnswerMap(sections: ExamSessionSection[]) {
   const map = new Map<number, ExamAnswer>();
   for (const sec of sections) {
     for (const q of sec.questions) {
+      // The backend `/api/exam/<id>/session` endpoint returns a
+      // `saved_answer` per question whenever a previous attempt is
+      // resumed (browser refresh, network drop, accidental tab-close).
+      // Seed the local map from that value so the student picks up
+      // exactly where they left off — without this, autosaved answers
+      // were silently dropped on every reload.
+      const saved = (q as unknown as { saved_answer?: unknown }).saved_answer;
+      const flagged = Boolean(
+        (q as unknown as { flagged?: boolean }).flagged,
+      );
       map.set(q.id, {
         question_id: q.id,
-        answer: null,
-        flagged: false,
+        answer:
+          saved === undefined || saved === null
+            ? null
+            : (saved as ExamAnswer["answer"]),
+        flagged,
         time_spent_ms: 0,
       });
     }