Fix continue button position to replace submit button location

Repositioned Next Passage button to appear in Submit button's location
rather than after Show Hints button, maintaining consistent layout
where Show Hints stays in rightmost position.

index.html

@@ -51,13 +51,13 @@
             <button type="button" id="submit-btn" class="typewriter-button">
                 Submit
             </button>
+            <button type="button" id="next-btn" class="typewriter-button hidden">
+                Next Passage
+            </button>
             <div class="controls-divider"></div>
             <button type="button" id="hint-btn" class="typewriter-button">
                 Show Hints
             </button>
-            <button type="button" id="next-btn" class="typewriter-button hidden">
-                Next Passage
-            </button>
         </div>
     </div>