feat(custom-widgets): Full Mantine v9 + SubFetch support for custom JSX (#6304)

vitest.setup.node.ts

@@ -0,0 +1,6 @@
+// Server packages validate their environment during module initialization.
+// Keep deterministic, non-secret values here so focused Node suites collect
+// without requiring a developer's local .env file.
+process.env.DB_DRIVER ??= "better-sqlite3";
+process.env.DB_URL ??= ":memory:";
+process.env.SECRET_ENCRYPTION_KEY ??= "0".repeat(64);