feat: resolve and display article titles for naddr references

- Add articleTitleResolver service to fetch article titles from relays
- Extract naddr identifiers from markdown content
- Fetch article titles in parallel using relay pool
- Replace naddr references with actual article titles
- Fallback to identifier if title fetch fails
- Update markdown processing to be async for title resolution
- Pass relayPool through component tree to enable resolution

Example: nostr:naddr1... now shows as "My Article Title" instead of "article:identifier"

Improves readability by showing human-friendly article titles in cross-references

src/components/ThreePaneLayout.tsx

@@ -302,6 +302,7 @@ const ThreePaneLayout: React.FC<ThreePaneLayoutProps> = (props) => {
               currentUserPubkey={props.currentUserPubkey}
               followedPubkeys={props.followedPubkeys}
               settings={props.settings}
+              relayPool={props.relayPool}
             />
           )}
         </div>