Refactor database test setup to use DB_PATH from vitest.config.js

web/server/__tests__/db.test.js

@@ -12,11 +12,8 @@ import fs from 'fs';
 import os from 'os';
 import path from 'path';
 
-// ── Set DB_PATH before db.js is imported ───────────────────────────────
-const TMP_DB = path.join(os.tmpdir(), `inv-test-${process.pid}.db`);
-process.env.DB_PATH = TMP_DB;
-
-// Now import (module-level side effect opens the DB at TMP_DB)
+// DB_PATH is set via vitest.config.js env before this module loads.
+const TMP_DB = process.env.DB_PATH;
 import db from '../db.js';
 import {
   saveItems, loadItems,