for #24718: add two remote firefox wallpapers

app/src/main/java/org/mozilla/fenix/wallpapers/Wallpaper.kt

@@ -58,6 +58,16 @@ sealed class Wallpaper {
         ) : Remote() {
             override val remoteParentDirName: String = "house"
         }
+
+        /**
+         * Wallpapers that are original Firefox creations.
+         */
+        data class Firefox(
+            override val name: String,
+        ) : Remote() {
+            override val expirationDate: Date? = null
+            override val remoteParentDirName: String = "firefox"
+        }
     }
 
     companion object {

app/src/main/java/org/mozilla/fenix/wallpapers/WallpaperManager.kt

@@ -243,6 +243,12 @@ class WallpaperManager(
             Wallpaper.Remote.House(
                 "mei",
             ),
+            Wallpaper.Remote.Firefox(
+                "twilight-hills"
+            ),
+            Wallpaper.Remote.Firefox(
+                "beach-vibe"
+            ),
         )
         private val availableWallpapers = listOf(defaultWallpaper) + localWallpapers + remoteWallpapers
         private const val ANIMATION_DELAY_MS = 1500L