refactor(leads): combine QR and Search buttons into a single toggle

- Simplified Tab 2 interface by replacing segmented control with a single toggle button.
- Updated button labels and icons to indicate the available switch action.

src/routes/events/[event_id]/(leads)/leads/exhibit/[exhibit_id]/ae_tab__add.svelte

@@ -30,25 +30,20 @@
 </script>
 
 <div class="ae-tab-add flex flex-col items-center space-y-6 w-full mx-auto">
-    <!-- Mode Toggle - Stable Width -->
-    <div class="flex p-1 bg-surface-200-800 rounded-xl w-full max-w-md shadow-inner">
+    <!-- Mode Toggle - Combined Button -->
+    <div class="flex justify-center w-full">
         <button 
             type="button" 
-            class="flex-1 btn btn-sm py-3 flex items-center justify-center gap-2 rounded-lg transition-all duration-200"
-            class:preset-filled-primary={mode === 'qr'}
-            onclick={() => set_mode('qr')}
+            class="btn btn-sm variant-filled-secondary font-bold shadow-md px-6 py-3 flex items-center gap-2 transition-all duration-200"
+            onclick={() => set_mode(mode === 'qr' ? 'search' : 'qr')}
         >
-            <QrCode size="1.2em" />
-            <span class="font-bold">Scan QR</span>
-        </button>
-        <button 
-            type="button" 
-            class="flex-1 btn btn-sm py-3 flex items-center justify-center gap-2 rounded-lg transition-all duration-200"
-            class:preset-filled-primary={mode === 'search'}
-            onclick={() => set_mode('search')}
-        >
-            <Search size="1.2em" />
-            <span class="font-bold">Search</span>
+            {#if mode === 'qr'}
+                <Search size="1.2em" />
+                <span>Switch to Manual Search</span>
+            {:else}
+                <QrCode size="1.2em" />
+                <span>Switch to QR Scan</span>
+            {/if}
         </button>
     </div>