feat: add unit tests (Rust parser+DB, Vitest frontend) and test workflow

vite.config.ts

@@ -1,3 +1,4 @@
+/// <reference types="vitest" />
 import { defineConfig } from "vite";
 import react from "@vitejs/plugin-react";
 import tailwindcss from "@tailwindcss/vite";
@@ -9,6 +10,12 @@ const host = process.env.TAURI_DEV_HOST;
 export default defineConfig(async () => ({
   plugins: [react(), tailwindcss()],
 
+  test: {
+    environment: "jsdom",
+    globals: true,
+    setupFiles: ["./src/test-setup.ts"],
+  },
+
   // Vite options tailored for Tauri development and only applied in `tauri dev` or `tauri build`
   //
   // 1. prevent Vite from obscuring rust errors