Custom Frutiger Aero 404

app/not-found.tsx renders a standalone screen: the root layout's ice
scene is the backdrop, the glass card/rim/bubbles come from the shared
recipes (full Aero with that theme on, frosted glass in light/dark),
and the mascot is the scene's glossy ice orb at full strength with a
snowflake and a "404" chip. Two ways out - back to the library and
into the chat - both 44px targets, en + cs.

The regression suite pins the 404 status, both links and the Czech
copy; the pixel-contrast scan covers the screen in all three themes.
The service worker no longer caches non-OK navigations as the offline
shell (a typo'd URL used to write the error page into the shell
cache). Version 0.5.6, SW -> freezmo-v78.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "freezmo",
-  "version": "0.5.5",
+  "version": "0.5.6",
   "private": true,
   "license": "GPL-3.0-only",
   "scripts": {