Add service worker implementation and tests for PWA caching strategy

- Implemented a service worker (sw.js) that handles installation, activation, and fetch events.
- Added caching logic for public assets and a fallback for offline navigation.
- Created unit tests (sw.test.ts) to validate service worker behavior, including asset caching, navigation handling, and activation logic.
- Ensured that private API routes and third-party requests are excluded from caching.

build.ts

@@ -1,6 +1,7 @@
 import tailwind from "bun-plugin-tailwind";
 import { rm, mkdir, copyFile } from "node:fs/promises";
 import path from "node:path";
+import { buildPwa } from "./scripts/build-pwa";
 
 const outdir = path.join(process.cwd(), "dist");
 await rm(outdir, { recursive: true, force: true });
@@ -36,3 +37,5 @@ await mkdir(path.join(outdir, "fonts/browser"), { recursive: true });
 for (const file of ["InstrumentSerif-Regular", "InstrumentSerif-Italic", "NotoSans-Regular", "NotoSans-Medium", "NotoSans-SemiBold"]) {
   await copyFile(`src/assets/fonts/${file}.woff2`, path.join(outdir, `fonts/browser/${file}.woff2`));
 }
+
+await buildPwa(outdir, result.outputs);