[feat] Add active jobs display to grid view (#8209)

## Summary
Show active jobs in grid view matching the list view behavior, with
refactored component structure.

## Changes
- **ActiveJobCard**: New component for grid view job display with
progress bar
- **AssetsSidebarGridView**: Extracted grid view logic from
AssetsSidebarTab (matching ListView pattern)
- **Progress styling**: Use `useProgressBarBackground` composable for
consistent progress bar styling
- **Assets header**: Add "Generated/Imported assets" header in grid view

src/utils/queueUtil.ts

@@ -1,6 +1,15 @@
 import type { TaskItemImpl } from '@/stores/queueStore'
 import type { JobState } from '@/types/queue'
 
+/**
+ * Checks if a job state represents an active (in-progress) job.
+ */
+export function isActiveJobState(state: JobState): boolean {
+  return (
+    state === 'pending' || state === 'initialization' || state === 'running'
+  )
+}
+
 /**
  * Map a task to a UI job state, including initialization override.
  *