refactor: use npm_package_version env var for API version

Replaces the readFileSync/path gymnastics with the simpler
npm_package_version environment variable that npm injects at runtime.

apps/api/src/routes/about.ts

@@ -1,13 +1,7 @@
-import { readFileSync } from "node:fs";
-import { dirname, join } from "node:path";
-import { fileURLToPath } from "node:url";
 import { Hono } from "hono";
 import type { AboutResponse, GiteaRelease } from "@elysium/types";
 
-const __dirname = dirname(fileURLToPath(import.meta.url));
-const { version: API_VERSION } = JSON.parse(
-  readFileSync(join(__dirname, "../../../package.json"), "utf-8"),
-) as { version: string };
+const API_VERSION = process.env.npm_package_version ?? "unknown";
 
 const GITEA_RELEASES_URL =
   "https://git.nhcarrigan.com/api/v1/repos/nhcarrigan-ideation/elysium/releases";