ui(footer): move "Built with hubris" byline into LeftSidebar

Pulled the hubris/Roman-year line out of the TopBar and into a new
Footer component rendered below the Settings button in the left
sidebar bottom panel, where it reads as a quiet attribution rather
than competing with the title plate up top.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/layout/LeftSidebar.tsx

@@ -27,6 +27,7 @@ import {
   Download as DownloadIcon,
 } from 'lucide-react'
 import { DateRangePicker } from '../filter/DateRangePicker'
+import { Footer } from './Footer'
 import { cn } from '@/lib/utils'
 import { sourceFolders, photos as photosApi, downloads, type FolderTreeNode } from '../../services/api'
 import { useMutation, useQueryClient } from '@tanstack/react-query'
@@ -639,6 +640,7 @@ export function LeftSidebar() {
             const showOnFolders =
               isSectionHeader && item.id === 'folders' && scanActivity.active
             const showOnFolderRow =
+              scanActivity.isScanning &&
               !!item.path &&
               !!scanActivity.currentFolder &&
               scanActivity.currentFolder.startsWith(item.path)
@@ -943,6 +945,8 @@ export function LeftSidebar() {
             Settings
           </button>
         )}
+
+        <Footer />
       </div>
 
       <DeleteFolderDialog