fix: update Clerk auth to use networkless JWT verification

- Replace deprecated verifySession() with verifyToken()
- Use JWT-based authentication (networkless verification)
- Update Clerk secret key to correct test key
- Fixes 410 Gone error from deprecated endpoint

This resolves the authentication issues with file uploads.

server/src/middleware/auth.ts

@@ -26,10 +26,10 @@ export const requireAuth = async (
 
     const token = authHeader.substring(7);
     
-    // Verify the session token with Clerk
-    const session = await clerkClient.sessions.verifySession(token, token);
+    // Verify the session token using networkless verification (JWT)
+    const payload = await clerkClient.verifyToken(token);
     
-    if (!session) {
+    if (!payload || !payload.sub) {
       return res.status(401).json({
         error: {
           code: 'INVALID_TOKEN',
@@ -39,8 +39,8 @@ export const requireAuth = async (
       });
     }
 
-    // Attach user ID to request
-    req.userId = session.userId;
+    // Attach user ID to request (sub is the user ID in JWT)
+    req.userId = payload.sub;
     
     next();
   } catch (error) {