fix(oauth): persist providerSpecificData from token refresh in health check

The health check refresh path was silently dropping result.providerSpecificData,
so resourceUrl (returned by Qwen on token refresh) was never persisted to the DB.
Now deep-merges refresh result providerSpecificData into the existing connection data.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/tokenHealthCheck.ts

@@ -282,6 +282,13 @@ async function checkConnection(conn) {
       updateData.tokenExpiresAt = new Date(Date.now() + result.expiresIn * 1000).toISOString();
     }
 
+    if (result.providerSpecificData) {
+      updateData.providerSpecificData = {
+        ...(conn.providerSpecificData || {}),
+        ...result.providerSpecificData,
+      };
+    }
+
     await updateProviderConnection(conn.id, updateData);
     log(`${LOG_PREFIX} ✓ ${conn.provider}/${conn.name || conn.email || conn.id} refreshed`);
   } else {