Fix to use the stored data

src/services/locale.ts

@@ -22,12 +22,21 @@ export async function getUserLocale(): Promise<Locale> {
         const res = await internal.get("/user", await authCookieHeader());
         const userLocale = res.data?.data?.locale;
         if (userLocale && locales.includes(userLocale as Locale)) {
-            // Set the cookie so subsequent requests don't need the API call
+            // Try to cache in a cookie so subsequent requests skip the API
-            (await cookies()).set(COOKIE_NAME, userLocale, {
+            // call. cookies().set() is only permitted in Server Actions and
-                maxAge: COOKIE_MAX_AGE,
+            // Route Handlers — not during rendering — so we isolate it so
-                path: "/",
+            // that a write failure doesn't prevent the locale from being
-                sameSite: "lax"
+            // returned for the current request.
-            });
+            try {
+                (await cookies()).set(COOKIE_NAME, userLocale, {
+                    maxAge: COOKIE_MAX_AGE,
+                    path: "/",
+                    sameSite: "lax"
+                });
+            } catch {
+                // Cannot set cookies in this context (e.g. during rendering);
+                // the correct locale is still returned below.
+            }
             return userLocale as Locale;
         }
     } catch {