Add reset button and make re-roll append results

- Reset button clears mood text, runtime filter, kid-friendly toggle,
  and returns to the empty state
- Show Me More now appends new cards below existing results instead
  of replacing them

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/static/index.html

@@ -90,6 +90,9 @@
                     <button id="surprise-btn" class="text-xs px-3 py-1 rounded-full border border-indigo-600/50 text-indigo-400 hover:bg-indigo-600/20 transition-colors">
                         Surprise Me
                     </button>
+                    <button id="reset-btn" class="text-xs px-3 py-1 rounded-full border border-gray-700 text-gray-500 hover:text-gray-300 hover:border-gray-500 transition-colors">
+                        Reset
+                    </button>
                 </div>
             </div>