refactor(ui): move logout button to top-right of app

- Move logout IconButton from sidebar to App component
- Position logout button fixed at top-right corner
- Remove onLogout prop from Bookmarks and BookmarkList components
- Clean up sidebar header by removing logout button
- Add app-header CSS with fixed positioning and high z-index

src/components/BookmarkList.tsx

@@ -1,15 +1,13 @@
 import React from 'react'
 import { FontAwesomeIcon } from '@fortawesome/react-fontawesome'
-import { faChevronLeft, faChevronRight, faRightFromBracket } from '@fortawesome/free-solid-svg-icons'
+import { faChevronLeft, faChevronRight } from '@fortawesome/free-solid-svg-icons'
 import { Bookmark, ActiveAccount } from '../types/bookmarks'
 import { BookmarkItem } from './BookmarkItem'
 import { formatDate, renderParsedContent } from '../utils/bookmarkUtils'
-import IconButton from './IconButton'
 
 interface BookmarkListProps {
   bookmarks: Bookmark[]
   activeAccount: ActiveAccount | null
-  onLogout: () => void
   formatUserDisplay: () => string
   onSelectUrl?: (url: string) => void
   isCollapsed: boolean
@@ -19,7 +17,6 @@ interface BookmarkListProps {
 export const BookmarkList: React.FC<BookmarkListProps> = ({ 
   bookmarks, 
   activeAccount, 
-  onLogout, 
   formatUserDisplay,
   onSelectUrl,
   isCollapsed,
@@ -57,13 +54,6 @@ export const BookmarkList: React.FC<BookmarkListProps> = ({
           >
             <FontAwesomeIcon icon={faChevronLeft} />
           </button>
-          <IconButton
-            icon={faRightFromBracket}
-            onClick={onLogout}
-            title="Logout"
-            ariaLabel="Logout"
-            variant="ghost"
-          />
         </div>
       </div>
       

src/components/Bookmarks.tsx

@@ -3,20 +3,17 @@ import { Hooks } from 'applesauce-react'
 import { useEventModel } from 'applesauce-react/hooks'
 import { Models } from 'applesauce-core'
 import { RelayPool } from 'applesauce-relay'
-import { faRightFromBracket } from '@fortawesome/free-solid-svg-icons'
 import { Bookmark } from '../types/bookmarks'
 import { BookmarkList } from './BookmarkList'
 import { fetchBookmarks } from '../services/bookmarkService'
 import ContentPanel from './ContentPanel'
 import { fetchReadableContent, ReadableContent } from '../services/readerService'
-import IconButton from './IconButton'
 
 interface BookmarksProps {
   relayPool: RelayPool | null
-  onLogout: () => void
 }
 
-const Bookmarks: React.FC<BookmarksProps> = ({ relayPool, onLogout }) => {
+const Bookmarks: React.FC<BookmarksProps> = ({ relayPool }) => {
   const [bookmarks, setBookmarks] = useState<Bookmark[]>([])
   const [loading, setLoading] = useState(true)
   const [selectedUrl, setSelectedUrl] = useState<string | undefined>(undefined)
@@ -106,13 +103,6 @@ const Bookmarks: React.FC<BookmarksProps> = ({ relayPool, onLogout }) => {
               <p className="user-info">Logged in as: {formatUserDisplay()}</p>
             )}
           </div>
-          <IconButton
-            icon={faRightFromBracket}
-            onClick={onLogout}
-            title="Logout"
-            ariaLabel="Logout"
-            variant="ghost"
-          />
         </div>
         <div className="loading">Loading bookmarks...</div>
       </div>
@@ -125,7 +115,6 @@ const Bookmarks: React.FC<BookmarksProps> = ({ relayPool, onLogout }) => {
         <BookmarkList 
           bookmarks={bookmarks}
           activeAccount={activeAccount || null}
-          onLogout={onLogout}
           formatUserDisplay={formatUserDisplay}
           onSelectUrl={handleSelectUrl}
           isCollapsed={isCollapsed}