added api logic, vitest, minimal testing ui

api/vitest.config.ts

@@ -0,0 +1,14 @@
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  test: {
+    environment: "node",
+    include: ["tests/**/*.test.ts"],
+    // run single-threaded to keep DB tests deterministic
+    pool: "threads",
+    poolOptions: { threads: { singleThread: true } },
+    testTimeout: 30_000,
+    env: { NODE_ENV: "test" },
+    setupFiles: ['tests/setup.ts'],
+  },
+});