✨ Add narrator texts infrastructure with API (Story 3.1)

- Create narrator_texts table migration with context/hero_type indexes
- Add NarratorText model with getRandomText() for variant selection
- Add NarratorTextSeeder with 30+ texts for 11 contexts
- Implement vouvoiement (recruteur) vs tutoiement (client/dev)
- Create NarratorController with GET /api/narrator/{context}
- Add useFetchNarratorText composable for frontend

Contexts: intro, transitions, hints, encouragements, contact_unlocked, welcome_back

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/implementation-artifacts/sprint-status.yaml

@@ -71,7 +71,7 @@ development_status:
   # EPIC 3: Navigation Gamifiée & Progression
   # ═══════════════════════════════════════════════════════════════════════════
   epic-3: in-progress
-  3-1-table-narrator-texts-api-narrateur: ready-for-dev
+  3-1-table-narrator-texts-api-narrateur: review
   3-2-composant-narratorbubble-le-bug: ready-for-dev
   3-3-textes-narrateur-contextuels-arc-revelation: ready-for-dev
   3-4-barre-progression-globale-xp-bar: ready-for-dev