Move test utilities from lib/ to test/ directory

- Rename `lib/test-preload.ts` → `test/preload.ts` and
  `lib/test-utils.ts` → `test/sqlite.ts`
- Update `bunfig.toml` preload path to `./test/preload.ts`
- Update all service test imports from `@/lib/test-utils` to
  `@/test/sqlite`

bunfig.toml

@@ -1,2 +1,2 @@
 [test]
-preload = ["./lib/test-preload.ts"]
+preload = ["./test/preload.ts"]