feat(planner): use cuisine gradient as fallback when no protein tag

Fallback chain: heroImageUrl → protein gradient → cuisine gradient → surface.
Also rename --gradient-cuisine-italienisch → --gradient-cuisine-deutsch
(actual seed tag) with an earthy warm-grey colour.

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

frontend/src/lib/design-system/tokens.test.ts

@@ -64,7 +64,7 @@ const requiredTokens = [
 	'--gradient-protein-kaese',
 	'--gradient-protein-huelsenfruechte',
 	// Cuisine gradient tokens
-	'--gradient-cuisine-italienisch',
+	'--gradient-cuisine-deutsch',
 	'--gradient-cuisine-asiatisch',
 	'--gradient-cuisine-indisch',
 	'--gradient-cuisine-mexikanisch',

frontend/src/lib/planner/DesktopDayTile.svelte

@@ -84,6 +84,10 @@
 		if (proteinTag?.name) {
 			return `var(--gradient-protein-${toCssKey(proteinTag.name)})`;
 		}
+		const cuisineTag = slot.recipe.tags?.find((t) => t.tagType === 'cuisine');
+		if (cuisineTag?.name) {
+			return `var(--gradient-cuisine-${toCssKey(cuisineTag.name)})`;
+		}
 		return 'var(--color-surface)';
 	})());
 </script>