fix(lint): resolve all linting and TypeScript errors

src/App.tsx

@@ -126,7 +126,7 @@ function App() {
                     relayPool={relayPool}
                     onLogout={() => {
                       if (accountManager) {
-                        accountManager.setActive(null)
+                        accountManager.setActive(undefined as never)
                         localStorage.removeItem('active')
                         console.log('Logged out')
                       }

src/components/BookmarkList.tsx

@@ -64,8 +64,6 @@ export const BookmarkList: React.FC<BookmarkListProps> = ({
       <SidebarHeader 
         onToggleCollapse={onToggleCollapse} 
         onLogout={onLogout}
-        viewMode={viewMode}
-        onViewModeChange={onViewModeChange}
         onOpenSettings={onOpenSettings}
         onRefresh={onRefresh}
         isRefreshing={isRefreshing}

src/components/ContentPanel.tsx

@@ -75,8 +75,6 @@ const ContentPanel: React.FC<ContentPanelProps> = ({
     return sourceHtml
   }, [html, renderedHtml, markdown, relevantHighlights, showUnderlines, highlightStyle])
 
-  // Check if we need to wait for HTML conversion
-  const needsHtmlConversion = markdown && !renderedHtml
 
   // Attach click handlers to highlight marks
   useEffect(() => {
@@ -191,7 +189,7 @@ const ContentPanel: React.FC<ContentPanelProps> = ({
           <div 
             ref={contentRef} 
             className="reader-html" 
-            dangerouslySetInnerHTML={{ __html: finalHtml || html }} 
+            dangerouslySetInnerHTML={{ __html: finalHtml || html || '' }} 
           />
         )
       ) : (