fix: Prevent text selection in MediaAssetCard (#6708)

## Summary
- Prevent text selection when clicking or dragging MediaAssetCard
- Add `select-none` Tailwind class to prevent unwanted text highlighting

## Changes
- Changed class from `gap-1` to `gap-1 select-none` in MediaAssetCard
container

## Problem
When users click or drag on a MediaAssetCard, the text content (tags,
titles, descriptions, buttons) gets selected and highlighted, which
creates a poor user experience.

## Solution
Added the `select-none` Tailwind CSS class which applies `user-select:
none` to prevent text selection within the card during mouse
interactions.

## Test plan
- [x] Click on MediaAssetCard and verify text is not selected
- [x] Drag across MediaAssetCard and verify text is not highlighted
- [x] Verify card selection still works properly
- [x] Verify buttons and interactive elements still work

🤖 Generated with [Claude Code](https://claude.com/claude-code)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6708-fix-Prevent-text-selection-in-MediaAssetCard-2ac6d73d365081f6bec2ffebad7cb7ed)
by [Unito](https://www.unito.io)

Co-authored-by: Claude <noreply@anthropic.com>

Author: viva-jinyi

src/platform/assets/components/MediaAssetCard.vue

@@ -248,7 +248,7 @@ provide(MediaAssetKey, {
 
 const containerClasses = computed(() =>
   cn(
-    'gap-1',
+    'gap-1 select-none',
     selected
       ? 'border-3 border-zinc-900 dark-theme:border-white bg-zinc-200 dark-theme:bg-zinc-700'
       : 'hover:bg-zinc-100 dark-theme:hover:bg-zinc-800'