✨ 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>

api/database/seeders/DatabaseSeeder.php

@@ -17,6 +17,7 @@ class DatabaseSeeder extends Seeder
             ProjectSeeder::class,
             SkillProjectSeeder::class,
             TestimonialSeeder::class,
+            NarratorTextSeeder::class,
         ]);
     }
 }