fix: vitrine/marketing pages use visitor's browser locale, not always English (v0.78.0)

getMarketingLocale() only ever read the marketing_locale cookie, defaulting anonymous first-time visitors to English until they manually used the language switcher — even though the switcher and a full French translation already existed. Now falls back to parsing Accept-Language when no cookie is set; an explicit switcher choice still wins on every later visit.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/lib/changelog.ts

@@ -1,5 +1,5 @@
 // Mirrors CHANGELOG.md at the repo root — update both together.
-export const APP_VERSION = "0.77.0";
+export const APP_VERSION = "0.78.0";
 
 export type ChangelogEntry = {
   version: string;
@@ -11,6 +11,13 @@ export type ChangelogEntry = {
 };
 
 export const CHANGELOG: ChangelogEntry[] = [
+  {
+    version: "0.78.0",
+    date: "2026-07-24 13:40",
+    fixed: [
+      "Marketing/vitrine pages now honor a first-time visitor's browser language (Accept-Language) instead of always defaulting to English until they manually switch. An explicit choice from the language switcher still wins on every later visit.",
+    ],
+  },
   {
     version: "0.77.0",
     date: "2026-07-24 13:00",