feat: Generation Page AI workflows + AI/Vector modules + exam session fixes

Generation Page (complete rebuild):
- Full production-parity exam generation wizard with 4 IELTS modules
- Reading: AI passage gen, 5 exercise types (MCQ, Fill, Write, T/F, Match)
- Listening: 4 section types, AI context gen, TTS audio gen (ElevenLabs)
- Writing: Task 1/2, AI instruction gen, word limits, marks
- Speaking: 3 parts, AI script gen, avatar video gen (7 avatars)
- Per-module config: timer, CEFR difficulty, access, approval, rubrics
- Exam submission workflow (draft/published)

Exam Structures:
- New encoach.exam.structure model + CRUD controller
- ExamStructuresPage wired to real API

AI Module (encoach_ai):
- OpenAI service, ElevenLabs TTS, AWS Polly, ELAI avatars
- AI settings model with Odoo config parameters
- 7 generation endpoints (passage, exercises, instructions, scripts, context)

Vector Module (encoach_vector):
- pgvector integration for RAG-based content search
- Embedding service with sentence-transformers

Exam Session Fixes:
- Fixed ExamSession.tsx field mapping (question_type→type, exam_title→title)
- Fixed submit payload to include attempt_id and answers
- Fixed normalizeType to handle null/undefined

Tested: 12/12 API tests passed, browser-verified with real OpenAI calls
Made-with: Cursor

src/pages/student/ExamSession.tsx

@@ -22,8 +22,8 @@ import { ScrollArea } from "@/components/ui/scroll-area";
 import { Flag, ChevronLeft, ChevronRight, Pause, Play } from "lucide-react";
 import { cn } from "@/lib/utils";
 
-function normalizeType(t: string) {
-  return t.toLowerCase().replace(/\s+/g, "_");
+function normalizeType(t: string | null | undefined) {
+  return (t ?? "").toLowerCase().replace(/\s+/g, "_");
 }
 
 function countWords(s: string) {
@@ -49,10 +49,26 @@ export default function ExamSession() {
   const { examId: examIdParam } = useParams();
   const examId = Number(examIdParam);
   const navigate = useNavigate();
-  const { data: session, isLoading, isError } = useExamSession(examId);
+  const { data: rawSession, isLoading, isError } = useExamSession(examId);
   const autoSave = useExamAutoSave();
   const submitMut = useExamSubmit();
 
+  const session = useMemo(() => {
+    if (!rawSession) return rawSession;
+    const raw = rawSession as any;
+    return {
+      ...raw,
+      title: raw.title || raw.exam_title || "",
+      sections: (raw.sections || []).map((s: any) => ({
+        ...s,
+        questions: (s.questions || []).map((q: any) => ({
+          ...q,
+          type: q.type || q.question_type || q.skill || "",
+        })),
+      })),
+    } as typeof rawSession;
+  }, [rawSession]);
+
   const [sectionIdx, setSectionIdx] = useState(0);
   const [questionIdx, setQuestionIdx] = useState(0);
   const [answers, setAnswers] = useState<Map<number, ExamAnswer>>(new Map());
@@ -121,10 +137,11 @@ export default function ExamSession() {
 
   useEffect(() => {
     if (!session || !section) return;
+    const attemptId = (session as any)?.attempt_id;
     const id = window.setInterval(() => {
       autoSave.mutate({
         examId,
-        payload: { section_id: section.id, answers: currentSectionAnswers() },
+        payload: { attempt_id: attemptId, section_id: section.id, answers: currentSectionAnswers() },
       });
     }, 10000);
     return () => window.clearInterval(id);
@@ -439,12 +456,20 @@ export default function ExamSession() {
             <Button
               type="button"
               onClick={() => {
-                submitMut.mutate(examId, {
-                  onSuccess: () => {
-                    setReviewOpen(false);
-                    navigate(`/student/exam/${examId}/status`);
+                const attemptId = (session as any)?.attempt_id;
+                const allAnswers = Array.from(answers.entries()).map(([qId, a]) => ({
+                  question_id: qId,
+                  answer: a.answer ?? "",
+                }));
+                submitMut.mutate(
+                  { examId, attempt_id: attemptId, answers: allAnswers },
+                  {
+                    onSuccess: () => {
+                      setReviewOpen(false);
+                      navigate(`/student/exam/${examId}/status`);
+                    },
                   },
-                });
+                );
               }}
               disabled={submitMut.isPending}
             >