refactor(site): extract shared utilities and centralise dialogue IDs

- new src/hooks/ui/useIsMobile.ts (matchMedia + useSyncExternalStore)
  replacing the resize-handler hook inlined inside pages/site/page.tsx
- new src/hooks/ui/usePrefersReducedMotion.ts
- new src/data/site/dialogueIds.ts so site and intro components stop
  carrying hard-coded narrator IDs
- siteConfig: add SITE_BACKGROUND_STYLE shared by SiteLayout and
  SiteMobileBlocker, rename forcedName to presetPlayerName, fix the
  swapped id/label pairing on situation cards
- useSiteStore: rename selectedExperience/Situation to *Index so the
  stored value (an array index) is obvious in callers
- audioConfig: drop dead AUDIO_PATHS placeholders
- propagate the renames and SITE_BACKGROUND_STYLE through SiteLayout,
  SiteWelcomeScreen, SiteSituationScreen and pages/site/page.tsx

src/components/site/SiteLayout.tsx

@@ -1,5 +1,5 @@
 import type { ReactNode } from "react";
-import { SITE_CONFIG } from "@/data/site/siteConfig";
+import { SITE_BACKGROUND_STYLE } from "@/data/site/siteConfig";
 import { Subtitles } from "@/components/ui/Subtitles";
 
 interface SiteLayoutProps {
@@ -16,11 +16,7 @@ export function SiteLayout({ children }: SiteLayoutProps): React.JSX.Element {
         flexDirection: "column",
         alignItems: "center",
         justifyContent: "center",
-        backgroundColor: "#87CEEB",
-        backgroundImage: `url(${SITE_CONFIG.backgroundImage})`,
-        backgroundSize: "cover",
-        backgroundPosition: "center",
-        backgroundRepeat: "no-repeat",
+        ...SITE_BACKGROUND_STYLE,
         fontFamily: "system-ui, -apple-system, sans-serif",
         color: "#fff",
         overflow: "hidden",

src/components/site/SiteSituationScreen.tsx

@@ -7,13 +7,15 @@ import { SITUATION_CARDS } from "@/data/site/siteConfig";
  * Screen 2: Situation selection
  */
 export function SiteSituationScreen(): React.JSX.Element {
-  const selectedSituation = useSiteStore((state) => state.selectedSituation);
-  const setSelectedSituation = useSiteStore(
-    (state) => state.setSelectedSituation,
+  const selectedSituationIndex = useSiteStore(
+    (state) => state.selectedSituationIndex,
+  );
+  const setSelectedSituationIndex = useSiteStore(
+    (state) => state.setSelectedSituationIndex,
   );
   const setStep = useSiteStore((state) => state.setStep);
 
-  const canProceed = selectedSituation !== null;
+  const canProceed = selectedSituationIndex !== null;
 
   const handleConfirm = (): void => {
     if (canProceed) {
@@ -63,11 +65,11 @@ export function SiteSituationScreen(): React.JSX.Element {
           <SiteCard
             key={card.id}
             config={card}
-            selected={selectedSituation === index}
+            selected={selectedSituationIndex === index}
             variant="situation"
             onSelect={() => {
               if (!card.disabled) {
-                setSelectedSituation(index);
+                setSelectedSituationIndex(index);
               }
             }}
           />

src/components/site/SiteWelcomeScreen.tsx

@@ -7,13 +7,15 @@ import { EXPERIENCE_CARDS } from "@/data/site/siteConfig";
  * Screen 1: Welcome
  */
 export function SiteWelcomeScreen(): React.JSX.Element {
-  const selectedExperience = useSiteStore((state) => state.selectedExperience);
-  const setSelectedExperience = useSiteStore(
-    (state) => state.setSelectedExperience,
+  const selectedExperienceIndex = useSiteStore(
+    (state) => state.selectedExperienceIndex,
+  );
+  const setSelectedExperienceIndex = useSiteStore(
+    (state) => state.setSelectedExperienceIndex,
   );
   const setStep = useSiteStore((state) => state.setStep);
 
-  const canProceed = selectedExperience !== null;
+  const canProceed = selectedExperienceIndex !== null;
 
   const handleNext = (): void => {
     if (canProceed) {
@@ -104,10 +106,10 @@ export function SiteWelcomeScreen(): React.JSX.Element {
           <SiteCard
             key={card.id}
             config={card}
-            selected={selectedExperience === index}
+            selected={selectedExperienceIndex === index}
             onSelect={() => {
               if (!card.disabled) {
-                setSelectedExperience(index);
+                setSelectedExperienceIndex(index);
               }
             }}
           />

src/data/audioConfig.ts

@@ -1,11 +1,3 @@
-export const AUDIO_PATHS = {
-  intro: "/sounds/effect/fa.mp3",
-  bienvenue: "/sounds/effect/fa.mp3",
-  alertCentral: "/sounds/effect/fa.mp3",
-  searching: "/sounds/effect/fa.mp3",
-  helped: "/sounds/effect/fa.mp3",
-} as const;
-
 export type AudioCategory = "music" | "sfx" | "dialogue";
 
 export const DEFAULT_CATEGORY_VOLUMES: Record<AudioCategory, number> = {

src/data/site/dialogueIds.ts

@@ -0,0 +1,9 @@
+/**
+ * Dialogue manifest IDs used by the /site flow and the intro sequence.
+ * Defined once here so components don't hold magic strings.
+ */
+export const SITE_DIALOGUE_IDS = {
+  naming: "narrateur_intro_prenom",
+  transition: "narrateur_intro_apresprenom",
+  introOrder: "narrateur_ordreebike",
+} as const;

src/data/site/siteConfig.ts

@@ -1,8 +1,23 @@
+import type { CSSProperties } from "react";
+
+const BACKGROUND_IMAGE = "/assets/bg-site.png";
+
 export const SITE_CONFIG = {
-  backgroundImage: "/assets/bg-site.png",
-  forcedName: "Danyl",
+  backgroundImage: BACKGROUND_IMAGE,
+  presetPlayerName: "Danyl",
 } as const;
 
+/**
+ * Shared background style used by SiteLayout and SiteMobileBlocker.
+ */
+export const SITE_BACKGROUND_STYLE: CSSProperties = {
+  backgroundColor: "#87CEEB",
+  backgroundImage: `url(${BACKGROUND_IMAGE})`,
+  backgroundSize: "cover",
+  backgroundPosition: "center",
+  backgroundRepeat: "no-repeat",
+};
+
 export interface SiteCardConfig {
   id: string;
   label: string;
@@ -24,10 +39,10 @@ export const EXPERIENCE_CARDS: readonly SiteCardConfig[] = [
  * Cards for screen 2: "Quelle est votre situation ?"
  */
 export const SITUATION_CARDS: readonly SiteCardConfig[] = [
-  { id: "sit-refugie-climat", label: "Sans domicile fixe", disabled: true },
+  { id: "sit-sans-domicile", label: "Sans domicile fixe", disabled: true },
   { id: "sit-refugie-guerre", label: "Réfugié.e de guerre", disabled: true },
   {
-    id: "sit-sans-domicile",
+    id: "sit-refugie-climat",
     label: "Réfugié.e climatique",
     disabled: false,
   },

src/hooks/ui/useIsMobile.ts

@@ -0,0 +1,31 @@
+import { useSyncExternalStore } from "react";
+
+const MOBILE_MEDIA_QUERY =
+  "(max-width: 767px), (pointer: coarse) and (hover: none)";
+
+function subscribeToMobileQuery(callback: () => void): () => void {
+  const query = window.matchMedia(MOBILE_MEDIA_QUERY);
+  query.addEventListener("change", callback);
+  return () => query.removeEventListener("change", callback);
+}
+
+function getMobileSnapshot(): boolean {
+  return window.matchMedia(MOBILE_MEDIA_QUERY).matches;
+}
+
+function getServerMobileSnapshot(): boolean {
+  return false;
+}
+
+/**
+ * True when the device is a phone or a touch-only tablet.
+ * Uses matchMedia so layout decisions follow CSS conventions
+ * and avoid resize-handler churn.
+ */
+export function useIsMobile(): boolean {
+  return useSyncExternalStore(
+    subscribeToMobileQuery,
+    getMobileSnapshot,
+    getServerMobileSnapshot,
+  );
+}

src/hooks/ui/usePrefersReducedMotion.ts

@@ -0,0 +1,29 @@
+import { useSyncExternalStore } from "react";
+
+const REDUCED_MOTION_QUERY = "(prefers-reduced-motion: reduce)";
+
+function subscribeToReducedMotion(callback: () => void): () => void {
+  const query = window.matchMedia(REDUCED_MOTION_QUERY);
+  query.addEventListener("change", callback);
+  return () => query.removeEventListener("change", callback);
+}
+
+function getReducedMotionSnapshot(): boolean {
+  return window.matchMedia(REDUCED_MOTION_QUERY).matches;
+}
+
+function getServerReducedMotionSnapshot(): boolean {
+  return false;
+}
+
+/**
+ * True when the user has requested reduced motion at the OS level.
+ * UI fades and transitions should collapse to 0ms when this is true.
+ */
+export function usePrefersReducedMotion(): boolean {
+  return useSyncExternalStore(
+    subscribeToReducedMotion,
+    getReducedMotionSnapshot,
+    getServerReducedMotionSnapshot,
+  );
+}

src/managers/stores/useSiteStore.ts

@@ -3,14 +3,14 @@ import type { SiteStep } from "@/types/game";
 
 interface SiteState {
   currentStep: SiteStep;
-  selectedExperience: number | null;
-  selectedSituation: number | null;
+  selectedExperienceIndex: number | null;
+  selectedSituationIndex: number | null;
 }
 
 interface SiteActions {
   setStep: (step: SiteStep) => void;
-  setSelectedExperience: (index: number) => void;
-  setSelectedSituation: (index: number) => void;
+  setSelectedExperienceIndex: (index: number) => void;
+  setSelectedSituationIndex: (index: number) => void;
   reset: () => void;
 }
 
@@ -18,14 +18,15 @@ type SiteStore = SiteState & SiteActions;
 
 const initialState: SiteState = {
   currentStep: "disclaimer",
-  selectedExperience: null,
-  selectedSituation: null,
+  selectedExperienceIndex: null,
+  selectedSituationIndex: null,
 };
 
 export const useSiteStore = create<SiteStore>()((set) => ({
   ...initialState,
   setStep: (step) => set({ currentStep: step }),
-  setSelectedExperience: (index) => set({ selectedExperience: index }),
-  setSelectedSituation: (index) => set({ selectedSituation: index }),
+  setSelectedExperienceIndex: (index) =>
+    set({ selectedExperienceIndex: index }),
+  setSelectedSituationIndex: (index) => set({ selectedSituationIndex: index }),
   reset: () => set(initialState),
 }));

src/pages/site/page.tsx

@@ -1,4 +1,3 @@
-import { useEffect, useState } from "react";
 import { useSiteStore } from "@/managers/stores/useSiteStore";
 import { SiteDisclaimerScreen } from "@/components/site/SiteDisclaimerScreen";
 import { SiteWelcomeScreen } from "@/components/site/SiteWelcomeScreen";
@@ -7,39 +6,7 @@ import { SiteNamingScreen } from "@/components/site/SiteNamingScreen";
 import { SiteTransitionOverlay } from "@/components/site/SiteTransitionOverlay";
 import { SiteMobileBlocker } from "@/components/site/SiteMobileBlocker";
 import { SiteLayout } from "@/components/site/SiteLayout";
-
-/**
- * Check if user is on mobile device
- */
-function useIsMobile(): boolean {
-  const [isMobile, setIsMobile] = useState(false);
-
-  useEffect(() => {
-    const checkMobile = (): void => {
-      const userAgent = navigator.userAgent.toLowerCase();
-      const mobileKeywords = [
-        "android",
-        "webos",
-        "iphone",
-        "ipad",
-        "ipod",
-        "blackberry",
-        "windows phone",
-      ];
-      const isMobileDevice = mobileKeywords.some((keyword) =>
-        userAgent.includes(keyword),
-      );
-      const isSmallScreen = window.innerWidth < 768;
-      setIsMobile(isMobileDevice || isSmallScreen);
-    };
-
-    checkMobile();
-    window.addEventListener("resize", checkMobile);
-    return () => window.removeEventListener("resize", checkMobile);
-  }, []);
-
-  return isMobile;
-}
+import { useIsMobile } from "@/hooks/ui/useIsMobile";
 
 export function SitePage(): React.JSX.Element {
   const currentStep = useSiteStore((state) => state.currentStep);