Add graph query optimization for faster social graph operations

- Add GraphQueryService for NIP-XX graph queries
- Add GraphCacheService for IndexedDB caching of results
- Optimize FollowedBy component with graph queries
- Add graph query support to ThreadService
- Add useFetchFollowGraph hook
- Add graph query toggle in Settings > System
- Bump version to v0.4.0

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

Co-Authored-By: Claude <noreply@anthropic.com>

src/components/Help/index.tsx

@@ -33,7 +33,7 @@ export default function Help() {
               <div className="space-y-2">
                 <KeyBinding keys={['↑', '↓']} altKeys={['k', 'j']} description={t('Move between items in a list')} />
                 <KeyBinding keys={['Tab']} description={t('Switch to next column (Shift+Tab for previous)')} />
-                <KeyBinding keys={['Page Up', 'Page Down']} description={t('Jump to top or bottom of list')} />
+                <KeyBinding keys={['Page Up']} description={t('Jump to top and focus first item')} />
               </div>
               <p className="font-medium mt-4">{t('Actions:')}</p>
               <div className="space-y-2">