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/SettingsPage.tsx

@@ -38,7 +38,7 @@ export default function SettingsPage() {
         </TabsList>
 
         <TabsContent value="codes" className="mt-4 space-y-4">
-          <AiTipBanner tip="2 batch codes have been unused for over 30 days. Consider sending reminder emails to the assigned entities or recycling unused codes." variant="insight" />
+          <AiTipBanner context="settings-codes" variant="insight" />
           <div className="flex gap-2">
             <Button size="sm"><Plus className="h-4 w-4 mr-1" /> Generate Single</Button>
             <Button size="sm" variant="outline"><Copy className="h-4 w-4 mr-1" /> Generate Batch</Button>
@@ -66,7 +66,7 @@ export default function SettingsPage() {
         </TabsContent>
 
         <TabsContent value="packages" className="mt-4 space-y-4">
-          <AiTipBanner tip="Based on conversion data, the IELTS Pro package has the highest ROI. Consider increasing the Corporate Bundle discount to 30% to boost enterprise sign-ups." variant="recommendation" />
+          <AiTipBanner context="settings-packages" variant="recommendation" />
           <div className="grid grid-cols-1 md:grid-cols-3 gap-4">
             {packages.map((p) => (
               <Card key={p.id} className="border-0 shadow-sm">
@@ -84,7 +84,7 @@ export default function SettingsPage() {
         </TabsContent>
 
         <TabsContent value="grading" className="mt-4 space-y-4">
-          <AiTipBanner tip="Current 0.5 increment scoring aligns with official IELTS band scoring. AI recommends keeping this configuration for standardised assessment." variant="tip" />
+          <AiTipBanner context="settings-grading" variant="tip" />
           <Card className="border-0 shadow-sm max-w-lg">
             <CardHeader><CardTitle className="text-base">Scoring Scale</CardTitle></CardHeader>
             <CardContent className="space-y-4">