feat: Add generation time sort options to Media Asset Panel (#6698)

## Summary
Add generation time-based sorting options to the Media Asset Panel

## Changes
- **New sorting options**:
  - Generation time (longest first) - Sort by longest execution time
  - Generation time (fastest first) - Sort by shortest execution time

- **Show only in Generated tab**: 
- Generation time sorting is only meaningful for output assets with
`executionTimeInSeconds` metadata
  - Implemented conditional rendering via `showGenerationTimeSort` prop

## Technical Details
- `useMediaAssetFiltering.ts`: 
  - Added `'longest'` and `'fastest'` to `SortOption` type
  - Added `getAssetExecutionTime` helper function
  - Implemented sorting logic using switch-case pattern
  
- `MediaAssetSortMenu.vue`: 
  - Added `showGenerationTimeSort` prop
- Generation time sort buttons placed inside `<template
v-if="showGenerationTimeSort">`
  
- `MediaAssetFilterBar.vue`: 
- Receives `showGenerationTimeSort` prop and passes it to
`MediaAssetSortMenu`
  
- `AssetsSidebarTab.vue`: 
- Passes `showGenerationTimeSort` prop based on `activeTab === 'output'`
  
- `src/locales/en/main.json`: 
  - Added `sortLongestFirst`: "Generation time (longest first)"
  - Added `sortFastestFirst`: "Generation time (fastest first)"

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

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

src/components/sidebar/tabs/AssetsSidebarTab.vue

@@ -36,13 +36,14 @@
       </div>
       <!-- Normal Tab View -->
       <TabList v-else v-model="activeTab" class="pt-4 pb-1">
-        <Tab value="input">{{ $t('sideToolbar.labels.imported') }}</Tab>
         <Tab value="output">{{ $t('sideToolbar.labels.generated') }}</Tab>
+        <Tab value="input">{{ $t('sideToolbar.labels.imported') }}</Tab>
       </TabList>
       <!-- Filter Bar -->
       <MediaAssetFilterBar
         v-model:search-query="searchQuery"
         v-model:sort-by="sortBy"
+        :show-generation-time-sort="activeTab === 'output'"
       />
     </template>
     <template #body>