✨ 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>

frontend/app/composables/useFetchNarratorText.ts

@@ -0,0 +1,53 @@
+export type NarratorContext =
+  | 'intro'
+  | 'transition_projects'
+  | 'transition_skills'
+  | 'transition_testimonials'
+  | 'transition_journey'
+  | 'hint'
+  | 'encouragement_25'
+  | 'encouragement_50'
+  | 'encouragement_75'
+  | 'contact_unlocked'
+  | 'welcome_back'
+
+export type HeroType = 'recruteur' | 'client' | 'dev'
+
+export interface NarratorTextData {
+  context: string
+  text: string
+  variant: number
+  hero_type: HeroType | null
+}
+
+interface NarratorTextResponse {
+  data: NarratorTextData
+  meta: { lang: string }
+}
+
+export function useFetchNarratorText() {
+  const config = useRuntimeConfig()
+  const { locale } = useI18n()
+
+  async function fetchText(context: NarratorContext, heroType?: HeroType): Promise<NarratorTextData | null> {
+    try {
+      const url = heroType
+        ? `/narrator/${context}?hero=${heroType}`
+        : `/narrator/${context}`
+
+      const response = await $fetch<NarratorTextResponse>(url, {
+        baseURL: config.public.apiUrl as string,
+        headers: {
+          'X-API-Key': config.public.apiKey as string,
+          'Accept-Language': locale.value,
+        },
+      })
+
+      return response.data
+    } catch {
+      return null
+    }
+  }
+
+  return { fetchText }
+}