feat(recipe): View-Beacon beim oeffnen der Detailseite

Fire-and-forget POST /api/recipes/[id]/view in onMount, nur wenn
profileStore.active gesetzt. Schreibt last_viewed_at fuers Profil —
Voraussetzung fuer den Sort 'Zuletzt angesehen' auf der Hauptseite.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/routes/recipes/[id]/+page.svelte

@@ -355,6 +355,17 @@
       }
     };
     document.addEventListener('visibilitychange', onVisibility);
+
+    // Track view per active profile (fire-and-forget). Skipped when no
+    // profile is active — we'd just be writing rows nobody can sort against later.
+    if (profileStore.active) {
+      void fetch(`/api/recipes/${data.recipe.id}/view`, {
+        method: 'POST',
+        headers: { 'content-type': 'application/json' },
+        body: JSON.stringify({ profile_id: profileStore.active.id })
+      });
+    }
+
     return () => document.removeEventListener('visibilitychange', onVisibility);
   });