bistro: fix PWA start_url and bump SW cache to v2

- manifest.json: start_url was '#/' (invalid per W3C spec — must be a
  URL path), causing the installed PWA to fail to launch on mobile
  Share > Add to Home Screen. Changed to './' so the OS opens
  index.html and the hash router takes over.
- sw.js: bump CACHE_NAME bistro-gem-v1 -> v2 so the activate handler
  flushes the old (broken) shell for users who already installed.

Author: sharpoverride

bistro/manifest.json

@@ -2,7 +2,7 @@
   "name": "Cămara Culinară",
   "short_name": "Bistro Gem",
   "description": "Cartea ta de bucate digitală, offline-first.",
-  "start_url": "#/",
+  "start_url": "./",
   "display": "standalone",
   "background_color": "#FCFAFA",
   "theme_color": "#D65A31",

bistro/sw.js

@@ -1,4 +1,4 @@
-const CACHE_NAME = 'bistro-gem-v1';
+const CACHE_NAME = 'bistro-gem-v2';
 const ASSETS = [
   './',
   './index.html',