fix: mobile tags pills show all active tags regardless of item count

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend-v2/src/lib/pages/brain/AtelierBrainPage.svelte

@@ -452,10 +452,9 @@
             </button>
           {/each}
           <span class="pill-separator"></span>
-          {#each sidebarTags.filter(t => t.is_active && t.item_count > 0) as tag}
+          {#each sidebarTags.filter(t => t.is_active) as tag}
             <button class="pill pill-tag" class:active={activeTag === tag.name} onclick={() => { activeTag = tag.name; activeTagId = tag.id; activeFolder = null; activeFolderId = null; loadItems(); }}>
               #{tag.name}
-              <span class="pill-count">{tag.item_count}</span>
             </button>
           {/each}
         </div>