fix(examples,auth-next): fix build issues and add missing config

- Fix Next.js version compatibility: downgrade auth-next packages to support Next 14+
- Add ESLint config for auth-next-default-test example
- Fix ESLint errors: escape quotes in JSX strings
- Fix CallbackPage props: add required config parameter with auto-detection
- Add type cast to resolve NextAuth config type conflicts
- Update pnpm-lock.yaml

Changes:
- auth-next-client/server: Next peerDependency now ^14.0.0 || ^15.0.0
- auth-next-client/server: devDependency downgraded to 14.2.25
- auth-next-default-test: add .eslintrc.json
- auth-next-default-test: fix JSX quote escaping
- auth-next-default-test: add auto-detected config to CallbackPage
- auth-next-default-test: add type cast to NextAuth call

These changes ensure the example app builds successfully in CI.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: rodrigo-fournier-immutable

.syncpackrc

@@ -13,6 +13,13 @@
       "dependencyTypes": ["peer"],
       "packages": ["@imtbl/auth-next-server", "@imtbl/auth-next-client", "@imtbl/sdk"],
       "isIgnored": true
+    },
+    {
+      "label": "Allow Next.js 14 in auth-next devDependencies for compatibility",
+      "dependencies": ["next"],
+      "dependencyTypes": ["dev"],
+      "packages": ["@imtbl/auth-next-server", "@imtbl/auth-next-client"],
+      "isIgnored": true
     }
   ]
 }