feat(offline)!: deploy-proof PWA cache + universal recipe loads

Service worker:
- Strip version suffix from CACHE_PAGES and CACHE_IMAGES so cached pages
  and recipe thumbs survive SW updates. Each deploy used to wipe both,
  forcing a re-sync before the user could open the app offline. Build
  and static caches stay version-suffixed (entries are hash-fingerprinted).
- Install precaches the offline shells: /, /rezepte, /recipes, both
  offline-shell pages, /glaube, /faith, /fitness — best-effort with
  Promise.allSettled so a single 5xx can't fail SW install.
- Bulk thumbnail precache now skips URLs already in CACHE_IMAGES.
  Recipe thumb URLs embed a content hash, so a cache hit guarantees
  identical bytes; subsequent syncs after small recipe edits no longer
  redownload every image.
- Activate cleanup deletes only stale versioned build/static entries
  and obsolete versioned pages/images caches.

Universal load migration:
- [recipeLang]/+layout.server.ts removed; logic in universal +layout.ts.
  Session fetched from /auth/session, nulled when offline.
- [recipeLang]/+page.server.ts and season/[month]/+page.server.ts
  removed; merged into universal +page.ts. Drops the __data.json
  round-trip entirely for these routes — IndexedDB fallback now runs
  even when the SW page cache is empty (fresh install, hash mismatch,
  etc.) instead of getting blocked by a 503 from the data handler.

Other:
- /static/rezepte/thumb URLs in sync.ts and the SW thumb fallback now
  use the absolute https://bocken.org origin. Dev/preview servers don't
  host /static/rezepte and were 404ing on themselves; production keys
  resolve to the same string so existing caches stay valid.
- Root +layout.svelte invalidateAll() now bails when !navigator.onLine.
  Resume-while-offline used to refetch every load() and surface the
  error page instead of the still-viewable cached content.

Bump 1.64.2 -> 1.65.2.

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "homepage",
-	"version": "1.64.2",
+	"version": "1.65.2",
 	"private": true,
 	"type": "module",
 	"scripts": {