build(vite): resolve @/ alias in main + preload configs

The four renderer vite configs all resolve "@" to ./src; main and preload
didn't, so any main-reachable file using @/ imports would break the
bundle. Mirror the same alias block in both configs and revert
lib/errors.ts + src/main/* to the project's @/ convention.

js/src/lib/errors.ts

@@ -1,5 +1,5 @@
 import { z } from "zod";
-import { appEnv } from "../config/env";
+import { appEnv } from "@/config/env";
 
 export class ApiError extends Error {
   constructor(