perf: add React.memo to heavy components for performance optimization

Wrap frequently re-rendered list item components with React.memo:
- TaskCard (renders 10-50+ times in Kanban board)
- DisplayConversationEntry (renders for every message in conversation)
- DiffCard (renders once per changed file)
- ProjectCard (renders in project grid)
- TaskRelationshipCard (renders in relationship lists)

Author: claude

frontend/src/components/DiffCard.tsx

@@ -1,7 +1,7 @@
 import { Diff } from 'shared/types';
 import { DiffModeEnum, DiffView, SplitSide } from '@git-diff-view/react';
 import { generateDiffFile, type DiffFile } from '@git-diff-view/file';
-import { useMemo } from 'react';
+import { memo, useMemo } from 'react';
 import { useUserSystem } from '@/components/config-provider';
 import { getHighLightLanguageFromPath } from '@/utils/extToLanguage';
 import { getActualTheme } from '@/utils/theme';
@@ -69,7 +69,7 @@ function readPlainLine(
   }
 }
 
-export default function DiffCard({
+const DiffCard = memo(function DiffCard({
   diff,
   expanded,
   onToggle,
@@ -323,4 +323,6 @@ export default function DiffCard({
       )}
     </div>
   );
-}
+});
+
+export default DiffCard;

frontend/src/components/NormalizedConversation/DisplayConversationEntry.tsx

@@ -1,3 +1,4 @@
+import { memo } from 'react';
 import { useTranslation } from 'react-i18next';
 import MarkdownRenderer from '@/components/ui/markdown-renderer.tsx';
 import {
@@ -602,7 +603,7 @@ export const DisplayConversationEntryMaxWidth = (props: Props) => {
   );
 };
 
-function DisplayConversationEntry({
+const DisplayConversationEntry = memo(function DisplayConversationEntry({
   entry,
   expansionKey,
   executionProcessId,
@@ -815,6 +816,6 @@ function DisplayConversationEntry({
       </div>
     </div>
   );
-}
+});
 
 export default DisplayConversationEntryMaxWidth;

frontend/src/components/projects/ProjectCard.tsx

@@ -21,7 +21,7 @@ import {
   Trash2,
 } from 'lucide-react';
 import { Project } from 'shared/types';
-import { useEffect, useRef } from 'react';
+import { memo, useEffect, useRef } from 'react';
 import { useTranslation } from 'react-i18next';
 import { useOpenProjectInEditor } from '@/hooks/useOpenProjectInEditor';
 import { useNavigateWithSearch } from '@/hooks';
@@ -35,7 +35,7 @@ type Props = {
   onEdit: (project: Project) => void;
 };
 
-function ProjectCard({
+const ProjectCard = memo(function ProjectCard({
   project,
   isFocused,
   fetchProjects,
@@ -144,6 +144,6 @@ function ProjectCard({
       </CardHeader>
     </Card>
   );
-}
+});
 
 export default ProjectCard;

frontend/src/components/tasks/TaskCard.tsx

@@ -1,4 +1,4 @@
-import { useCallback, useEffect, useRef, useState } from 'react';
+import { memo, useCallback, useEffect, useRef, useState } from 'react';
 import { KanbanCard } from '@/components/ui/shadcn-io/kanban';
 import { CheckCircle, Loader2, XCircle, Play } from 'lucide-react';
 import type { TaskWithAttemptStatus } from 'shared/types';
@@ -16,7 +16,7 @@ interface TaskCardProps {
   isOpen?: boolean;
 }
 
-export function TaskCard({
+export const TaskCard = memo(function TaskCard({
   task,
   index,
   status,
@@ -125,4 +125,4 @@ export function TaskCard({
     </KanbanCard>
     </div>
   );
-}
+});

frontend/src/components/tasks/TaskRelationshipCard.tsx

@@ -1,3 +1,4 @@
+import { memo } from 'react';
 import { Card } from '@/components/ui/card';
 import { Badge } from '@/components/ui/badge';
 import { cn } from '@/lib/utils';
@@ -10,7 +11,7 @@ interface TaskRelationshipCardProps {
   className?: string;
 }
 
-export function TaskRelationshipCard({
+export const TaskRelationshipCard = memo(function TaskRelationshipCard({
   task,
   isCurrentTask = false,
   onClick,
@@ -103,4 +104,4 @@ export function TaskRelationshipCard({
       </div>
     </Card>
   );
-}
+});