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

frontend/src/components/ai/AiStudyCoach.tsx

@@ -29,8 +29,11 @@ export default function AiStudyCoach() {
     suggestMutation.mutate();
   };
 
-  const suggestions = suggestMutation.data?.suggestions ?? [];
-  const planTips = suggestMutation.data?.study_plan_tips ?? [];
+  const d = suggestMutation.data;
+  const suggestions = d ? [d.suggestion, ...(d.focus_areas ?? []).map((a: string) => `Focus area: ${a}`)].filter(Boolean) : [];
+  const planTips = d?.daily_plan?.length
+    ? d.daily_plan.map((p: { activity: string; duration_min: number; skill: string }) => `${p.activity} (${p.duration_min}min — ${p.skill})`)
+    : d?.motivation ? [d.motivation] : [];
 
   return (
     <Card className="border-0 shadow-sm bg-primary/5">