[feat] Add right-click context menu to MediaAssetCard (#6844)

## Summary
- Add right-click context menu functionality to MediaAssetCard
- Separate context menu into its own component
(MediaAssetContextMenu.vue)
- Ensure only one context menu is visible at a time within the same tab

## Changes
- Add `MediaAssetContextMenu.vue` - new component for context menu
- Update `MediaAssetCard.vue` - show context menu on right-click and
more button click
- Delete `MediaAssetMoreMenu.vue` - consolidated into context menu
- Delete `MediaAssetButtonDivider.vue` - unused
- Update `AssetsSidebarTab.vue` - add context menu state management
- Refactor `useMediaAssetActions.ts`

## Screenshot

[screen-capture.webm](https://github.com/user-attachments/assets/6fe414ef-b134-4fbe-98aa-6437bb354b41)

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

---------

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

src/components/sidebar/tabs/AssetsSidebarTab.vue

@@ -85,13 +85,12 @@
               :show-output-count="shouldShowOutputCount(item)"
               :output-count="getOutputCount(item)"
               :show-delete-button="shouldShowDeleteButton"
-              :open-popover-id="openPopoverId"
+              :open-context-menu-id="openContextMenuId"
               @click="handleAssetSelect(item)"
               @zoom="handleZoomClick(item)"
               @output-count-click="enterFolderView(item)"
               @asset-deleted="refreshAssets"
-              @popover-opened="openPopoverId = item.id"
-              @popover-closed="openPopoverId = null"
+              @context-menu-opened="openContextMenuId = item.id"
             />
           </template>
         </VirtualGrid>
@@ -113,7 +112,7 @@
                       count: totalOutputCount
                     })
               "
-              type="transparent"
+              type="secondary"
               :class="isCompact ? 'text-left' : ''"
               @click="handleDeselectAll"
             />
@@ -202,8 +201,8 @@ const folderPromptId = ref<string | null>(null)
 const folderExecutionTime = ref<number | undefined>(undefined)
 const isInFolderView = computed(() => folderPromptId.value !== null)
 
-// Track which asset's popover is open (for single-instance popover management)
-const openPopoverId = ref<string | null>(null)
+// Track which asset's context menu is open (for single-instance context menu management)
+const openContextMenuId = ref<string | null>(null)
 
 // Determine if delete button should be shown
 // Hide delete button when in input tab and not in cloud (OSS mode - files are from local folders)