fix(FN-2859): reduce background AI pill height in executor footer

- Tighten background task indicator pill padding to reduce vertical footprint
- Lower line-height to keep icon/text alignment after the size reduction
- Reduce mobile min-height so the footer pill no longer appears oversized

packages/dashboard/app/components/BackgroundTasksIndicator.css

@@ -7,7 +7,7 @@
   display: inline-flex;
   align-items: center;
   gap: 6px;
-  padding: 2px 10px;
+  padding: 1px 8px;
   border-radius: 12px;
   border: 1px solid var(--border);
   background: var(--surface);
@@ -15,7 +15,7 @@
   cursor: pointer;
   font-size: 12px;
   font-weight: 500;
-  line-height: 20px;
+  line-height: 18px;
   white-space: nowrap;
   transition: background var(--transition-fast);
 }
@@ -120,7 +120,7 @@
   }
 
   .background-tasks-indicator__pill {
-    min-height: 36px;
+    min-height: 28px;
   }
 }