Gitignore generated public/sw.js

next.config.ts regenerates public/sw.js on every build with a new
timestamp; tracking it produces noise on every build. Add to .gitignore
and untrack — it is always regenerated by `pnpm dev` / `pnpm build`
and by the Docker build stage.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -9,6 +9,9 @@ dist/
 build/
 *.tsbuildinfo
 
+# Generated at build time by next.config.ts — do not commit
+public/sw.js
+
 # Auto-generated by Next.js — never edit, never commit
 next-env.d.ts