feat: add /me page to show user's recent highlights

- Create Me component to display logged-in user's highlights
- Add /me route to App routing
- Update SidebarHeader to navigate to /me when clicking profile avatar
- Integrate Me page in ThreePaneLayout (same as Settings/Explore)
- Show user profile info and highlight count
- List all highlights created by the user

Clicking the profile picture now takes you to your personal highlights page.

src/components/ThreePaneLayout.tsx

@@ -28,6 +28,7 @@ interface ThreePaneLayoutProps {
   isSidebarOpen: boolean
   showSettings: boolean
   showExplore?: boolean
+  showMe?: boolean
   
   // Bookmarks pane
   bookmarks: Bookmark[]
@@ -81,6 +82,9 @@ interface ThreePaneLayoutProps {
   
   // Optional Explore content
   explore?: React.ReactNode
+  
+  // Optional Me content
+  me?: React.ReactNode
 }
 
 const ThreePaneLayout: React.FC<ThreePaneLayoutProps> = (props) => {
@@ -288,6 +292,11 @@ const ThreePaneLayout: React.FC<ThreePaneLayoutProps> = (props) => {
             <>
               {props.explore}
             </>
+          ) : props.showMe && props.me ? (
+            // Render Me inside the main pane to keep side panels
+            <>
+              {props.me}
+            </>
           ) : (
             <ContentPanel 
               loading={props.readerLoading}